Magnetic Effects of Electric Current(image)

Magnetic Effect of Electric Current

⚡ The Magnetic Effect of Electric Current – An Introduction

In the previous chapter on Electricity, we explored the heating effects of electric current, which are widely used in devices like electric heaters, irons, and bulbs. But did you know that electric current has other significant effects too?

One of the most fascinating effects of electric current is its magnetic effect. When an electric current flows through a conductor, it produces a magnetic field around it, turning the wire into a temporary magnet. This phenomenon is the foundation of electromagnetism and is used in devices like electric bells, motors, generators, and transformers.

To understand this effect better, let’s perform a simple activity that demonstrates how an electric current-carrying wire behaves like a magnet. 🔍✨

📌 Magnetic Effect of Electric Current – Detailed Notes

🔋 Introduction

In the previous chapter on Electricity, we studied the heating effect of electric current.
Apart from heating, electric current also has a magnetic effect.
A current-carrying conductor produces a magnetic field around it.

🧪 Activity 13.1: Demonstrating the Magnetic Effect of Electric Current

Materials Required:

✔️ Thick copper wire
✔️ Battery or power source
✔️ Switch (key & plug)
✔️ Compass needle

Procedure:

1️⃣ Take a straight, thick copper wire and connect it between two points X and Y in an electric circuit.
2️⃣ Place the wire XY perpendicular to the plane of the paper.
3️⃣ Keep a small compass near the copper wire and note the position of its needle.
4️⃣ Pass electric current through the wire by inserting the key into the plug.
5️⃣ Observe the change in the compass needle’s position.

Observation:

✅ The compass needle gets deflected when current flows through the wire.

Conclusion:

📌 The deflection of the compass needle indicates that the current-carrying wire produces a magnetic field around it.
📌 This confirms that electricity and magnetism are linked.

🧲 Understanding Electromagnetism

The magnetic field is produced by the flow of electric current through a conductor.
This discovery led to the development of electromagnets, electric motors, and generators.
A moving magnet can also induce an electric current, which is the principle behind electric generators.

👨‍🔬 Hans Christian Oersted and His Contribution to Electromagnetism

🗓️ Born: 1777
🗓️ Died: 1851

🔹 In 1820, Hans Christian Oersted accidentally discovered that a compass needle deflected when an electric current passed through a nearby metallic wire.
🔹 This proved that electricity and magnetism are related.
🔹 His research laid the foundation for electromagnetism, leading to the invention of devices like:
✅ Radio 📻
✅ Television 📺
✅ Fiber optics 🌐

🔹 Unit of Magnetic Field Strength: Named Oersted (Oe) in his honor.

⚙️ Applications of the Magnetic Effect of Electric Current

✅ Electromagnets – Used in electric bells, magnetic cranes, and MRI machines.
✅ Electric Motors – Convert electrical energy into mechanical energy (e.g., fans, washing machines).
✅ Electric Generators – Convert mechanical energy into electrical energy.
✅ Transformers – Used in power distribution to regulate voltage.

🎯 Conclusion

Electricity and magnetism are interconnected phenomena.
A current-carrying wire produces a magnetic field, demonstrated through Oersted’s experiment.
This principle is the foundation of modern electrical and electronic devices.

📌 Magnetic Field and Field Lines – Detailed Notes

🧲 Introduction to Magnetic Field

A compass needle gets deflected when brought near a bar magnet because it is itself a small bar magnet.
The north-seeking end of the compass needle points towards the north pole of the Earth, and the south-seeking end points towards the south pole.
Fundamental Properties of Magnets:
✅ Like poles repel, while unlike poles attract each other.
✅ A magnetic field is the region around a magnet where its influence can be detected.
✅ Magnetic field lines help visualize the field and show the direction of the magnetic force.

🧪 Activity 13.2: Observing Magnetic Field Lines Using Iron Filings

Materials Required:

✔️ White sheet of paper
✔️ Drawing board
✔️ Bar magnet
✔️ Iron filings (can be sprinkled using a salt-sprinkler)

Procedure:

1️⃣ Fix a white sheet of paper on a drawing board using adhesive.
2️⃣ Place a bar magnet in the center of the paper.
3️⃣ Sprinkle iron filings uniformly around the magnet.
4️⃣ Gently tap the board.

Observation:

✅ The iron filings arrange themselves in a specific pattern around the magnet.
✅ The pattern reveals invisible magnetic field lines around the bar magnet.

Conclusion:

📌 The iron filings experience a force due to the magnetic field and align along its field lines.
📌 The region surrounding a magnet, where its force can be detected, is called the magnetic field.
📌 The lines along which the iron filings arrange are called magnetic field lines.

🧭 Activity 13.3: Drawing Magnetic Field Lines Using a Compass

Materials Required:

✔️ Bar magnet
✔️ White sheet of paper
✔️ Compass needle
✔️ Drawing board & adhesive

Procedure:

1️⃣ Fix a white sheet of paper on a drawing board and mark the boundary of the bar magnet.
2️⃣ Place a compass near the north pole of the magnet.
3️⃣ Observe that the south pole of the compass needle points towards the north pole of the magnet.
4️⃣ Mark the positions of the two ends of the compass needle.
5️⃣ Move the compass so that its south pole takes the previous position of its north pole.
6️⃣ Continue marking points till you reach the south pole of the magnet.
7️⃣ Join all the points with a smooth curve.
8️⃣ Repeat the process from different points around the magnet to obtain a pattern of magnetic field lines.

Observation:

✅ The compass needle aligns itself along curved lines around the magnet.
✅ The closer the lines, the stronger the magnetic field.
✅ The field lines always form closed loops.

Conclusion:

📌 The pattern of field lines shows the magnetic field around the magnet.
📌 The direction of the magnetic field is from the north pole to the south pole outside the magnet and from the south pole to the north pole inside the magnet.
📌 The magnetic field is strongest where the field lines are densest.

🔍 Properties of Magnetic Field Lines

1️⃣ Field lines originate from the north pole and end at the south pole.
2️⃣ Inside the magnet, the field lines travel from the south pole to the north pole, making them closed curves.
3️⃣ The strength of the magnetic field is indicated by the closeness of field lines:
✅ More crowded lines → Stronger magnetic field
✅ More spaced-out lines → Weaker magnetic field
4️⃣ Field lines never intersect because:

If they did, the compass needle would point in two different directions at the same point, which is impossible.

⚙️ Applications of Magnetic Field Lines

✅ Electromagnets – Used in electric bells, magnetic cranes, and MRI machines.
✅ Electric Motors – Convert electrical energy into mechanical energy.
✅ Electric Generators – Convert mechanical energy into electrical energy.
✅ Compass Navigation – Used for determining direction.

🎯 Key Takeaways

✔️ A magnetic field is the region where a magnet’s influence can be detected.
✔️ Magnetic field lines help visualize the direction and strength of the magnetic field.
✔️ The deflection of a compass needle is used to determine the magnetic field pattern.
✔️ The density of field lines indicates the strength of the magnetic field.
✔️ Magnetic field lines never cross each other.

❓ Q U E S T I O N & A N S W E R

🧭 1. Why does a compass needle get deflected when brought near a bar magnet? 🧲

✅ Answer:
A compass needle is a small bar magnet, with its north pole pointing towards the Earth's geographic north and south pole towards the Earth's geographic south. When a compass is brought near a bar magnet, the magnetic field of the bar magnet interacts with the magnetic field of the compass.

📌 Key Points:

🧲 The north pole of the compass is repelled by the north pole of the bar magnet and attracted to the south pole of the bar magnet.
🧭 Similarly, the south pole of the compass is repelled by the south pole of the bar magnet and attracted to the north pole.
🔄 This interaction causes the needle to deflect, aligning itself along the magnetic field lines of the bar magnet.

🧲 Conclusion:
The deflection of the compass needle confirms the presence of a magnetic field around the bar magnet.

📌 Magnetic Field Due to a Current-Carrying Conductor – Detailed Notes

🧲 Introduction

In Activity 13.1, we observed that a current-carrying conductor produces a magnetic field around it.
The pattern and direction of this magnetic field depend on the shape of the conductor.
The field can be visualized using iron filings and a compass needle.

🔍 13.2.1 Magnetic Field Due to a Current Through a Straight Conductor

Key Observations

1️⃣ A straight current-carrying wire generates a magnetic field around it.
2️⃣ The pattern of the field lines depends on the direction of the current.
3️⃣ The strength of the field increases with increasing current.
4️⃣ The field strength decreases as the distance from the conductor increases.

🧪 Activity 13.4: Observing Magnetic Field Using a Compass

Materials Required:

✔️ Long straight copper wire
✔️ Battery (cells of 1.5V each)
✔️ Plug key
✔️ Compass needle

Procedure:

1️⃣ Connect the battery, wire, and key in series.
2️⃣ Place the straight wire parallel to a compass needle.
3️⃣ Close the circuit by inserting the plug key.
4️⃣ Observe the direction of deflection of the compass needle.
5️⃣ Reverse the battery connections to change the current direction.
6️⃣ Observe the new deflection direction of the compass needle.

Observation:

✅ The compass needle deflects when current flows through the wire.
✅ When the current direction is reversed, the compass deflection also reverses.

Conclusion:

📌 Electric current produces a magnetic field, and the field direction depends on the current direction.

🧪 Activity 13.5: Visualizing Magnetic Field Lines Using Iron Filings

Materials Required:

✔️ Battery (12V)
✔️ Variable resistance (rheostat)
✔️ Ammeter (0–5A)
✔️ Plug key
✔️ Connecting wires
✔️ Long straight thick copper wire
✔️ Cardboard sheet
✔️ Iron filings

Procedure:

1️⃣ Insert a thick copper wire through the center of a rectangular cardboard.
2️⃣ Fix the cardboard so it does not slide up or down.
3️⃣ Connect the copper wire vertically in series with the battery and other components.
4️⃣ Sprinkle iron filings uniformly over the cardboard.
5️⃣ Close the key to allow current flow through the wire.
6️⃣ Gently tap the cardboard and observe the pattern formed by iron filings.

Observation:

✅ The iron filings arrange themselves in concentric circles around the wire.
✅ The concentric circles represent magnetic field lines around the conductor.
✅ The direction of magnetic field lines can be determined using a compass.
✅ Reversing the current reverses the magnetic field direction.

Conclusion:

📌 A current-carrying straight conductor creates a circular magnetic field around it.
📌 The field strength increases with current and decreases with distance.

🧭 Key Properties of Magnetic Field Around a Straight Conductor

1️⃣ The field lines form concentric circles around the conductor.
2️⃣ The direction of the field lines depends on the direction of current.
3️⃣ The strength of the magnetic field:
✅ Increases with increased current
✅ Decreases as distance from the wire increases
4️⃣ The direction of the field lines reverses when the current is reversed.

✋ 13.2.2 Right-Hand Thumb Rule

Definition:

📌 The Right-Hand Thumb Rule is a simple way to determine the direction of the magnetic field around a current-carrying conductor.

Rule Explanation:

✋ Imagine holding a current-carrying conductor in your right hand:

Thumb points in the direction of current.
Fingers curl around the conductor, indicating the direction of magnetic field lines.

Key Observations:

✅ If the current flows upwards, the magnetic field is counterclockwise.
✅ If the current flows downwards, the magnetic field is clockwise.
✅ The field lines form closed loops around the conductor.

Significance of the Right-Hand Thumb Rule:

✔️ Helps determine the magnetic field direction around a straight wire.
✔️ Essential for understanding electromagnetism and applications like motors and solenoids.

⚙️ Applications of Magnetic Field Due to a Current-Carrying Conductor

✅ Electric Motors – Converts electrical energy into mechanical motion.
✅ Electromagnets – Used in lifting heavy objects in scrapyards.
✅ Transformers – Used in power distribution.
✅ Induction Cookers – Work on the principle of magnetic field induction.

🎯 Key Takeaways

✔️ A current-carrying conductor produces a magnetic field around it.
✔️ The field forms concentric circles around a straight wire.
✔️ Right-Hand Thumb Rule helps determine the field direction.
✔️ The magnetic field strength depends on current and distance.

📌 Example 13.1: Direction of Magnetic Field Around a Power Line

❓ Problem Statement:
A current flows through a horizontal power line in the east-to-west direction. What is the direction of the magnetic field at a point directly below and directly above the power line?

✅ Solution:

1️⃣ The current flows from east to west.
2️⃣ Using the Right-Hand Thumb Rule:

Point the thumb of your right hand in the direction of the current (east to west).
Curl your fingers around the wire.
The fingers show the direction of the magnetic field.

🔄 Magnetic Field Direction:

At a point below the wire → Into the plane (clockwise when viewed from the east end).
At a point above the wire → Out of the plane (anti-clockwise when viewed from the west end).

📌 Conclusion:
✅ The magnetic field lines form concentric circles around the wire.
✅ The direction of the field depends on the position of observation.

❓ Q U E S T I O N S & A N S W E R S

🧲 1. Draw magnetic field lines around a bar magnet.

✅ Answer:

The magnetic field lines around a bar magnet emerge from the north pole and curve around to merge at the south pole.
Inside the magnet, the lines move from the south pole to the north pole, forming closed loops.
The field lines are denser near the poles, indicating a stronger magnetic field.

📌 Diagram Representation:

🧲 2. List the properties of magnetic field lines.

✅ Answer:
1️⃣ Closed Loops: Magnetic field lines emerge from the north pole and enter the south pole, forming closed curves inside the magnet.
2️⃣ No Intersection: Magnetic field lines never cross each other, as this would indicate two directions for the field at a single point, which is impossible.
3️⃣ Density and Strength: The closer the field lines, the stronger the magnetic field (strongest at the poles).
4️⃣ Direction: Field lines always move from the north pole to the south pole outside the magnet and from the south pole to the north pole inside the magnet.
5️⃣ Tangential Property: The tangent at any point on a field line gives the direction of the magnetic field at that point.

🧲 3. Why don’t two magnetic field lines intersect each other?

✅ Answer:

If two magnetic field lines intersected, a compass needle placed at the intersection would point in two different directions at the same time, which is impossible.
A magnetic field at any point has only one unique direction.
Therefore, magnetic field lines never cross each other.

📌 Conclusion: Magnetic field lines are continuous, non-intersecting curves that represent the direction and strength of a magnetic field. 🚀

📌 Magnetic Field Due to a Current Through a Circular Loop – Detailed Notes

🧲 Introduction

We have studied that a current-carrying straight wire produces a magnetic field around it.
But what happens when the straight wire is bent into a circular loop and current is passed through it?
The magnetic field lines around the loop form a different pattern compared to a straight conductor.

🔍 Key Observations

1️⃣ The magnetic field produced by a current-carrying wire decreases as distance increases.
2️⃣ In a circular loop, the concentric field lines become larger and larger as we move away from the wire.
3️⃣ At the center of the loop, these circular field lines appear as straight lines.
4️⃣ Every section of the wire contributes to the field at the center in the same direction, reinforcing the total field.
5️⃣ If a circular coil has ‘n’ turns, the total magnetic field is n times stronger than that of a single loop.

🧪 Activity 13.6: Observing Magnetic Field Due to a Circular Coil

Materials Required:

✔️ Rectangular cardboard (with two holes)
✔️ Circular coil (with a large number of turns)
✔️ Battery
✔️ Plug key
✔️ Rheostat (variable resistance)
✔️ Iron filings

Procedure:

1️⃣ Take a rectangular cardboard and make two holes.
2️⃣ Insert a circular coil through the holes such that it is normal to the plane of the cardboard.
3️⃣ Connect the coil in series with a battery, plug key, and rheostat.
4️⃣ Sprinkle iron filings uniformly on the cardboard.
5️⃣ Plug the key to allow current flow through the coil.
6️⃣ Gently tap the cardboard and observe the pattern of iron filings.

Observation:

✅ The iron filings align themselves along curved magnetic field lines around the coil.
✅ The field lines at the center of the loop appear straight, indicating a uniform magnetic field.
✅ The strength of the field increases with the number of turns in the coil.

✋ Right-Hand Thumb Rule for a Circular Loop

If you curl the fingers of your right hand in the direction of current flow in the circular loop:
✅ Your thumb points in the direction of the magnetic field at the center.

📌 Key Properties of the Magnetic Field in a Circular Loop

1️⃣ The magnetic field lines form concentric circles around each section of the wire.
2️⃣ At the center of the loop, the field lines appear as straight parallel lines, indicating a strong and uniform magnetic field.
3️⃣ The direction of the field at the center is determined by the Right-Hand Thumb Rule.
4️⃣ The strength of the magnetic field increases:
✅ With an increase in current.
✅ With an increase in the number of turns (n) in the coil.

⚙️ Applications of Magnetic Fields in Circular Loops

✅ Electromagnets – Used in electric bells, magnetic cranes, and MRI machines.
✅ Solenoids and Toroids – Used in transformers and inductors.
✅ Electric Motors and Generators – Function based on electromagnetic induction.

🎯 Key Takeaways

✔️ A circular current loop generates a magnetic field, with concentric field lines around the wire.
✔️ At the center of the loop, the field appears straight and uniform.
✔️ The strength of the magnetic field increases with current and number of turns (n).
✔️ The Right-Hand Thumb Rule helps determine the field direction.

📌 Magnetic Field Due to a Current in a Solenoid – Detailed Notes

🧲 What is a Solenoid?

A solenoid is a coil of many circular turns of insulated copper wire wound closely in the shape of a cylinder.
When current flows through a solenoid, it produces a magnetic field similar to that of a bar magnet.

🔍 Key Observations

1️⃣ The magnetic field lines around a current-carrying solenoid resemble those of a bar magnet.
2️⃣ One end of the solenoid acts as a north pole, and the other end acts as a south pole.
3️⃣ Inside the solenoid, the field lines are parallel, indicating a uniform magnetic field.
4️⃣ The magnetic field strength increases with:
✅ Increase in current.
✅ Increase in number of turns per unit length.
✅ Using a soft iron core inside the solenoid.

✋ Right-Hand Thumb Rule for a Solenoid

Curl the fingers of your right hand around the solenoid in the direction of current.
Your thumb points towards the north pole of the solenoid.

🧪 Magnetization Using a Solenoid (Electromagnet Formation)

A strong magnetic field inside a solenoid can magnetize soft iron when placed inside the coil.
This creates an electromagnet, which retains magnetism as long as current flows.
Electromagnets are widely used in various applications.

⚙️ Applications of Solenoids and Electromagnets

✅ Electromagnets – Used in electric bells, speakers, and scrapyard cranes.
✅ MRI Machines – Use strong magnetic fields for medical imaging.
✅ Electric Motors & Transformers – Work based on solenoid principles.
✅ Inductors & Relays – Essential in electrical circuits and devices.

🎯 Key Takeaways

✔️ A solenoid generates a magnetic field similar to a bar magnet.
✔️ The field is uniform inside the solenoid and stronger with more turns and current.
✔️ Soft iron cores inside solenoids create electromagnets.
✔️ The Right-Hand Thumb Rule determines the direction of the magnetic field.

❓ Q U E S T I O N S & A N S W E R S

🧲 1. Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.

✅ Answer:

Using the Right-Hand Thumb Rule:
- Curl the fingers of your right hand in the direction of the current (clockwise).
- Your thumb will point in the direction of the magnetic field inside the loop.

📌 Result:
✔ Inside the loop → The magnetic field is directed into the table (downward).
✔ Outside the loop → The magnetic field is directed out of the table (upward).

🧲 2. The magnetic field in a given region is uniform. Draw a diagram to represent it.

✅ Answer:

A uniform magnetic field is represented by parallel equidistant lines pointing in the same direction.
Example: The Earth's magnetic field or the field inside a solenoid.

📌 Diagram Representation:
(Draw parallel straight lines with arrows indicating the direction of the magnetic field.)

🧲 3. Choose the correct option.

The magnetic field inside a long straight solenoid-carrying current:
(a) is zero. ❌
(b) decreases as we move towards its end. ❌
(c) increases as we move towards its end. ❌
(d) is the same at all points. ✅

✅ Correct Answer: (d) is the same at all points.

❓ Q U E S T I O N S & A N S W E R S

✅ Answer:

Using the Right-Hand Thumb Rule:
- Curl the fingers of your right hand in the direction of the current (clockwise).
- Your thumb will point in the direction of the magnetic field inside the loop.

📌 Result:
✔ Inside the loop → The magnetic field is directed into the table (downward).
✔ Outside the loop → The magnetic field is directed out of the table (upward).

🧲 2. The magnetic field in a given region is uniform. Draw a diagram to represent it.

✅ Answer:

A uniform magnetic field is represented by parallel equidistant lines pointing in the same direction.
Example: The Earth's magnetic field or the field inside a solenoid.

📌 Diagram Representation:
→ → → → → → → → →

→ → → → → → → → →

🧲 3. Choose the correct option.

✅ Correct Answer: (d) is the same at all points.

📌 Explanation:
✔ Inside a long straight solenoid, the magnetic field is uniform and parallel.
✔ The field strength does not change at any point inside the solenoid.
✔ The field is strongest inside the solenoid and weaker outside.

📌 Force on a Current-Carrying Conductor in a Magnetic Field – Detailed Notes

🧲 Introduction

We know that an electric current flowing through a conductor produces a magnetic field.
This magnetic field can exert a force on a nearby magnet.
Andre Marie Ampere (1775–1836) suggested that if a magnet experiences a force due to a conductor, then the magnet must also exert an equal and opposite force on the current-carrying conductor.
This force can be demonstrated with Activity 13.7.

🧪 Activity 13.7: Observing Force on a Current-Carrying Conductor

Materials Required:

✔️ Small aluminium rod (AB) (~5 cm long)
✔️ Two connecting wires
✔️ Battery
✔️ Plug key
✔️ Rheostat (variable resistance)
✔️ Strong horseshoe magnet

Procedure:

1️⃣ Suspend the aluminium rod AB horizontally from a stand using two wires.
2️⃣ Place a strong horseshoe magnet so that:

The north pole is vertically below the rod.
The south pole is vertically above the rod.
This ensures the magnetic field is directed upwards.
3️⃣ Connect the aluminium rod in series with the battery, key, and rheostat.
4️⃣ Pass a current through the aluminium rod from end B to end A.
5️⃣ Observe the movement of the rod.

Observation:

✅ The rod is displaced towards the left when current flows from B to A.
✅ Reversing the current causes the rod to move towards the right.
✅ Reversing the magnetic field also reverses the direction of force.

Conclusion:

📌 A force is exerted on the current-carrying conductor when placed in a magnetic field.
📌 The direction of force depends on:
✅ The direction of the current.
✅ The direction of the magnetic field.
📌 The force is strongest when the current is perpendicular to the magnetic field.

✋ Fleming’s Left-Hand Rule

To determine the direction of force acting on the conductor, we use Fleming’s Left-Hand Rule:

📌 Rule Statement:

Stretch the thumb, forefinger, and middle finger of your left hand so that they are mutually perpendicular (at 90° to each other).
Index Finger (Forefinger) → Points in the direction of the magnetic field (N to S).
Middle Finger (Second Finger) → Points in the direction of current (positive to negative).
Thumb → Points in the direction of force (motion) on the conductor.

📌 Key Takeaways:
✔ The force is always perpendicular to both the current and the magnetic field.
✔ The direction of force reverses when either the current or magnetic field direction is reversed.

⚙️ Applications of Force on a Current-Carrying Conductor

✅ Electric Motors – Convert electrical energy into mechanical energy using this force.
✅ Electric Generators – Use electromagnetic induction to produce electricity.
✅ Loudspeakers & Microphones – Work on the interaction of current and magnetic fields.
✅ Measuring Instruments – Like galvanometers, function using this principle.

🎯 Key Takeaways

✔️ A current-carrying conductor experiences a force in a magnetic field.
✔️ The direction of force depends on current and magnetic field direction.
✔️ Fleming’s Left-Hand Rule helps determine the force direction.
✔️ This principle is used in motors, generators, and other electromagnetic devices.

📌 Example 13.2: Force on an Electron in a Magnetic Field

❓ Problem Statement:

An electron enters a magnetic field at right angles to it, as shown in Fig. 13.14. What is the direction of the force acting on the electron?

Options:

(a) To the right
(b) To the left
(c) Out of the page
(d) Into the page ✅

✅ Solution:

📌 Step 1: Understanding the Motion of the Electron

The electron is moving perpendicular to the magnetic field.
A moving charge in a magnetic field experiences a force (as per Fleming’s Left-Hand Rule).

📌 Step 2: Applying Fleming’s Left-Hand Rule

Forefinger (Index Finger) → Direction of Magnetic Field (B).
Middle Finger (Second Finger) → Direction of Current (I).
Thumb → Direction of Force (Motion).

📌 Step 3: Remembering Electron's Charge

Electrons have a negative charge, so their motion is opposite to conventional current.
The force direction obtained from Fleming’s Left-Hand Rule applies to positive charges.
Since the electron is negatively charged, the force direction is opposite to what is obtained by the rule.

📌 Final Answer:
✅ The force on the electron is directed into the page (Option d).

❓ Q U E S T I O N S & A N S W E R S

🧲 1. Which of the following properties of a proton can change while it moves freely in a magnetic field?
(There may be more than one correct answer.)

✅ Options:
(a) Mass ❌ (Mass remains constant as it is an intrinsic property of a proton.)
(b) Speed ❌ (A magnetic field does not change the speed of a charged particle, only its direction.)
(c) Velocity ✅ (Velocity changes because the direction of motion is altered by the magnetic force.)
(d) Momentum ✅ (Momentum changes because velocity changes.)

✅ Correct Answer: (c) Velocity and (d) Momentum

📌 Explanation:

A magnetic field exerts a force perpendicular to the motion of a charged particle.
This changes the direction of the proton’s velocity but not its speed.
Since momentum (p = mv) depends on velocity, it also changes.

🧲 2. In Activity 13.7, how do we think the displacement of rod AB will be affected if:

✅ (i) Current in rod AB is increased?

The displacement increases because the force on the rod is directly proportional to current $(F \propto I)$ .

✅ (ii) A stronger horseshoe magnet is used?

The displacement increases because a stronger magnetic field (B) increases the force $(F \propto B)$ .

✅ (iii) Length of the rod AB is increased?

The displacement increases because the force is also proportional to the length of the conductor in the field $(F \propto L)$ .

📌 Conclusion:
✔ More current, a stronger magnet, or a longer conductor all result in greater force and displacement of the rod.

🧲 3. A positively charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. What is the direction of the magnetic field?

✅ Options:
(a) Towards south ❌
(b) Towards east ❌
(c) Downward ❌
(d) Upward ✅

✅ Correct Answer: (d) Upward

📌 Explanation (Using Fleming’s Left-Hand Rule):

Index Finger (Forefinger) → Points in the direction of the magnetic field (B).
Middle Finger (Second Finger) → Points in the direction of current or motion of a positive charge (west).
Thumb → Points in the direction of the force (deflection) (north).

Since the thumb points north, the index finger (magnetic field direction) must be upward.

🚀 Conclusion: The magnetic field is directed upward.

🧲 Magnetism in Medicine – Detailed Notes

📌 Introduction

Electric current always produces a magnetic field.
Even weak ion currents in nerve cells generate magnetic fields in the human body.
These fields are extremely weak (~one-billionth of Earth's magnetic field).

🧠 Magnetism in the Human Body

🔹 Magnetic Fields in Nerve Cells

Nerve impulses (electric signals) travel along neurons to communicate with muscles.
These impulses generate tiny magnetic fields.

🔹 Major Organs with Significant Magnetic Fields

✔️ The Heart ❤️ – Produces strong magnetic fields due to electrical activity in cardiac muscles.
✔️ The Brain 🧠 – Nerve signals create measurable magnetic fields, which help in neurological studies.

🖥️ Magnetic Resonance Imaging (MRI)

MRI (Magnetic Resonance Imaging) is a medical imaging technique based on magnetic fields.
Strong magnetic fields interact with hydrogen atoms in the body, producing detailed internal images.
Applications:
✅ Brain scans 🧠 – Detects tumors, strokes, and brain injuries.
✅ Spinal cord imaging 🏥 – Diagnoses nerve disorders.
✅ Joint & Muscle scans 🦴 – Identifies injuries and inflammation.

⚕️ Importance of Magnetism in Medicine

✔️ Used in MRI scans for non-invasive medical imaging.
✔️ Helps diagnose heart & brain conditions.
✔️ Aids in neurological studies (e.g., EEG with magnetic sensors).
✔️ Research continues for magnetic therapy and treatment methods.

🎯 Key Takeaways

✔ Nerve signals generate weak magnetic fields.
✔ Heart & brain produce significant biomagnetic fields.
✔ MRI technology uses strong magnetic fields for medical imaging.
✔ Magnetism plays a crucial role in modern medicine.

📌 Electric Motor – Detailed Notes

⚡ What is an Electric Motor?

An electric motor is a device that converts electrical energy into mechanical energy.
It is widely used in:
✅ Electric fans
✅ Refrigerators
✅ Mixers & washing machines
✅ Computers & MP3 players

🛠️ Construction of an Electric Motor

An electric motor consists of the following key components:

1️⃣ Rectangular Coil (ABCD):

Made of insulated copper wire.
Placed between the poles of a magnetic field.
The arms AB and CD are perpendicular to the magnetic field direction.

2️⃣ Split Ring (Commutator):

The coil is connected to two halves P and Q of a split ring.
Inner sides of the split ring are insulated.
The split ring acts as a commutator, reversing the current direction every half turn.

3️⃣ Brushes (X and Y):

Stationary conducting brushes that maintain electrical contact with the rotating split ring.
They transfer current from the external circuit to the coil.

4️⃣ Magnetic Field:

Provided by permanent magnets or electromagnets.

5️⃣ Battery (Power Source):

Supplies direct current (DC) to the motor.

6️⃣ Axle (O):

The coil and axle are mounted freely to rotate.

🔄 Working of an Electric Motor

Step 1: Current Flow in the Coil

The current enters the motor through brush X and flows into the coil ABCD.
Current flows from A to B in arm AB and from C to D in arm CD (opposite directions).

Step 2: Force on the Coil (Fleming’s Left-Hand Rule)

Using Fleming’s Left-Hand Rule:
- Forefinger → Magnetic field direction (N to S).
- Middle finger → Current direction (positive to negative).
- Thumb → Direction of force (motion).
Effect on arms of the coil:
✅ Arm AB is pushed downward.
✅ Arm CD is pushed upward.
✅ The coil rotates anti-clockwise.

Step 3: Role of the Commutator (Reversal of Current)

After half a rotation, the split ring reverses contacts:
✅ Brush X now touches Q, and brush Y touches P.
✅ Current direction reverses (now flows DCBA instead of ABCD).
✅ Force directions are reversed:
- AB is pushed up.
- CD is pushed down.
This keeps the rotation continuous in the same direction.

🛠️ Enhancements in Commercial Motors

Commercial electric motors are more powerful due to:

1️⃣ Electromagnets instead of permanent magnets.
2️⃣ More turns of conducting wire in the coil to increase power.
3️⃣ Soft iron core (Armature) – enhances the magnetic effect.

⚙️ Applications of Electric Motors

✅ Fans & Air Conditioners – Convert electrical energy into rotation.
✅ Washing Machines & Mixers – Use rotating motion for mechanical work.
✅ Electric Vehicles – Motors drive the wheels.
✅ Robotics & Automation – Precise control of mechanical movement.

🎯 Key Takeaways

✔️ Electric motors convert electrical energy into mechanical energy.
✔️ Fleming’s Left-Hand Rule determines the direction of force.
✔️ A commutator (split ring) reverses current every half rotation for continuous motion.
✔️ Commercial motors use electromagnets, more coil turns, and an iron core for efficiency.

❓ Q U E S T I O N S & A N S W E R S

🧲 1. State Fleming’s Left-Hand Rule.

✅ Answer:
📌 Fleming’s Left-Hand Rule states that if you stretch the thumb, forefinger, and middle finger of your left hand such that they are mutually perpendicular (at 90° to each other):

Forefinger (Index Finger) → Points in the direction of the magnetic field (N to S).
Middle Finger (Second Finger) → Points in the direction of current (positive to negative).
Thumb → Points in the direction of motion (force) of the conductor.

📌 Application: Used to determine the direction of force in electric motors.

🧲 2. What is the principle of an electric motor?

✅ Answer:
📌 An electric motor works on the principle that a current-carrying conductor experiences a force when placed in a magnetic field.

The direction of this force is determined by Fleming’s Left-Hand Rule.
In a motor, this force causes the coil to rotate, converting electrical energy into mechanical energy.

🧲 3. What is the role of the split ring in an electric motor?

✅ Answer:
📌 The split ring in an electric motor acts as a commutator, which:

Reverses the direction of current every half rotation.
Ensures continuous rotation of the motor in the same direction.
Maintains contact with the external circuit through stationary brushes.

📌 Conclusion: The split ring ensures smooth and continuous functioning of the electric motor. 🚀

📌 Electromagnetic Induction – Detailed Notes

🧲 What is Electromagnetic Induction?

Electromagnetic induction is the process of generating electric current in a conductor by changing the magnetic field around it.
It was discovered by Michael Faraday in 1831.
This principle is the working basis of electric generators, transformers, and induction coils.

🧪 Activity 13.8: Induced Current by Moving a Magnet

Materials Required:

✔ Coil of wire (AB) with many turns
✔ Galvanometer
✔ Strong bar magnet

Procedure:

1️⃣ Connect the ends of the coil to a galvanometer.
2️⃣ Move the north pole of the magnet towards the coil.
3️⃣ Observe the galvanometer needle deflecting to one side (indicating current flow).
4️⃣ Stop moving the magnet – the needle returns to zero.
5️⃣ Move the north pole of the magnet away – the needle deflects in the opposite direction (opposite current flow).
6️⃣ Keep the magnet stationary – the galvanometer shows no deflection.

Observations:

✅ Moving the magnet induces a current in the coil.
✅ Reversing the motion reverses the direction of current.
✅ No motion = No current.

Conclusion:

📌 A changing magnetic field induces an electric current in the coil.
📌 This induced current is called electromagnetic induction.

🧑‍🔬 Michael Faraday and His Contribution

Born: 1791 | Died: 1867
Faraday’s key discoveries:
✅ Electromagnetic induction (basis of generators & transformers).
✅ Faraday’s Laws of Electrolysis.
Interesting Fact: Despite having no formal education, he made groundbreaking contributions to physics and chemistry.

🧪 Activity 13.9: Inducing Current Using a Second Coil

Materials Required:

✔ Two copper wire coils (one with 50 turns, one with 100 turns)
✔ Non-conducting cylindrical roll
✔ Battery and plug key
✔ Galvanometer

Procedure:

1️⃣ Insert two coils over a non-conducting cylindrical roll.
2️⃣ Connect Coil-1 to a battery and plug key.
3️⃣ Connect Coil-2 to a galvanometer.
4️⃣ Close the key (current starts flowing in Coil-1).
5️⃣ Observe the galvanometer – it momentarily deflects, indicating a current in Coil-2.
6️⃣ Disconnect Coil-1 – the galvanometer momentarily deflects in the opposite direction.
7️⃣ When current in Coil-1 becomes steady or zero, the galvanometer shows no deflection.

Observations:

✅ Changing current in Coil-1 induces a current in Coil-2.
✅ Steady current does not induce any current.

Conclusion:

📌 A changing magnetic field induces current in a nearby conductor.
📌 This process is called electromagnetic induction.
📌 The primary coil (Coil-1) produces a changing magnetic field, inducing current in the secondary coil (Coil-2).

✋ Fleming’s Right-Hand Rule

📌 To determine the direction of induced current, use Fleming’s Right-Hand Rule:

Forefinger (Index Finger) → Direction of magnetic field (B).
Thumb → Direction of motion of conductor.
Middle Finger (Second Finger) → Direction of induced current.

📌 Key Insight: The induced current is maximum when the conductor moves perpendicular to the magnetic field.

⚙️ Applications of Electromagnetic Induction

✅ Electric Generators – Convert mechanical energy into electrical energy.
✅ Transformers – Step up/down voltage in power distribution.
✅ Induction Stoves – Heat food using magnetic fields.
✅ Microphones & Speakers – Convert sound waves into electrical signals.

🎯 Key Takeaways

✔️ Electromagnetic induction occurs when a changing magnetic field induces current in a conductor.
✔️ Michael Faraday discovered this phenomenon in 1831.
✔️ Fleming’s Right-Hand Rule helps determine the direction of induced current.
✔️ This principle is used in generators, transformers, and other electrical devices.

❓ Q U E S T I O N & A N S W E R

🧲 1. Explain different ways to induce current in a coil.

✅ Answer:
Electromagnetic induction is the process of inducing current in a coil by changing the magnetic field around it. The current induced is called induced current.

📌 Different Ways to Induce Current in a Coil:

1️⃣ By Moving a Magnet Near the Coil

Moving a bar magnet towards the coil induces current in the coil.
Moving the magnet away induces current in the opposite direction.
Keeping the magnet stationary produces no current.

2️⃣ By Moving the Coil in a Magnetic Field

If the coil is moved into or out of a magnetic field, a current is induced.
Faster movement induces a stronger current.

3️⃣ By Changing the Current in a Nearby Coil

If a primary coil (connected to a battery) is placed near a secondary coil, changing the current in the primary coil induces a current in the secondary coil.
This happens because the magnetic field of the primary coil changes.

📌 Conclusion:
Induced current is generated whenever there is a change in the magnetic field around a conductor. This is the principle of electromagnetic induction, discovered by Michael Faraday. 🚀

📌 Electric Generator – Detailed Notes

⚡ What is an Electric Generator?

An electric generator is a device that converts mechanical energy into electrical energy using the principle of electromagnetic induction.
Large currents are produced for homes and industries by rotating a conductor in a magnetic field.

🛠️ Construction of an Electric Generator

An electric generator consists of the following key components:

1️⃣ Rectangular Coil (ABCD):

Made of insulated copper wire.
Rotates between the poles of a permanent magnet.

2️⃣ Rings (R₁ and R₂):

Two metallic rings connected to the ends of the coil.
Internally attached to an axle for rotation.
Help in transferring induced current to the external circuit.

3️⃣ Stationary Brushes (B₁ and B₂):

Conducting stationary brushes press against the rings.
Transfer induced current to the external circuit.

4️⃣ Magnetic Field:

Provided by a permanent magnet.

5️⃣ Axle:

Rotates the coil mechanically (by a turbine, hand crank, or motor).

6️⃣ Galvanometer:

Detects the flow and direction of current.

🔄 Working of an Electric Generator

Step 1: Rotation of Coil in the Magnetic Field

The axle rotates the coil ABCD clockwise.
Arm AB moves up, and arm CD moves down.

Step 2: Induced Current (Using Fleming’s Right-Hand Rule)

Index Finger (Forefinger) → Direction of magnetic field (B).
Thumb → Direction of motion of coil.
Middle Finger (Second Finger) → Direction of induced current.

✅ Induced Current Flow:
✔ When the coil rotates, an induced current is generated in direction ABCD.
✔ The external current flows from B₂ to B₁.

Step 3: Reversing the Current Direction (Alternating Current - AC)

After half a rotation,
✅ Arm CD moves up, and arm AB moves down.
✅ Induced current reverses direction to DCBA.
✅ External current now flows from B₁ to B₂.
This results in an alternating current (AC), where current reverses direction periodically.

🔀 Types of Electric Generators

1️⃣ AC Generator (Alternating Current Generator)

Uses two separate rings (R₁ and R₂).
Current reverses direction every half rotation.
Most power stations generate AC (used in homes and industries).

2️⃣ DC Generator (Direct Current Generator)

Uses a split-ring commutator instead of two separate rings.
Ensures current flows in one direction only.
Used in batteries, cars, and small electrical devices.

⚡ Difference Between AC and DC

Feature	Alternating Current (AC)	Direct Current (DC)
Direction of Flow	Changes periodically	Flows in one direction
Generated by	AC Generator	DC Generator
Transmission Loss	Less (can be transmitted over long distances)	More (not efficient for long distances)
Usage	Home appliances, industries	Batteries, electronic devices
Example	Power supply at home (50 Hz in India)	Batteries in cars and mobile phones

⚙️ Applications of Electric Generators

✅ Power Stations – Generate electricity for homes & industries.
✅ Wind Turbines – Convert wind energy into electrical energy.
✅ Hydroelectric Plants – Use water flow to rotate generators.
✅ Backup Generators – Provide power during outages.
✅ Bicycle Dynamos – Generate electricity for bicycle lights.

🎯 Key Takeaways

✔ Electric generators convert mechanical energy into electrical energy using electromagnetic induction.
✔ AC generators produce alternating current, while DC generators produce direct current.
✔ Fleming’s Right-Hand Rule determines the direction of induced current.
✔ AC is preferred for power distribution because it can be transmitted over long distances with minimal energy loss.

❓ Q U E S T I O N S & A N S W E R S

🧲 1. State the principle of an electric generator.

✅ Answer:
📌 An electric generator works on the principle of electromagnetic induction.

When a coil rotates in a magnetic field, the magnetic flux linked with the coil changes.
This change in magnetic flux induces an electric current in the coil.
The direction of the induced current is given by Fleming’s Right-Hand Rule.

🧲 2. Name some sources of direct current.

✅ Answer:
📌 Sources of direct current (DC) include:
✔ Batteries (Dry Cell, Lead-Acid Battery, Lithium-ion Battery)
✔ Solar Cells
✔ DC Generators
✔ Fuel Cells

🧲 3. Which sources produce alternating current?

✅ Answer:
📌 Sources of alternating current (AC) include:
✔ AC Generators (Alternators)
✔ Power Plants (Hydroelectric, Thermal, Nuclear, Wind Turbines)
✔ Inverters (Convert DC to AC)

🧲 4. Choose the correct option:
A rectangular coil of copper wire is rotated in a magnetic field. The direction of the induced current changes once in each:

✅ Options:
(a) Two revolutions ❌
(b) One revolution ❌
(c) Half revolution ✅
(d) One-fourth revolution ❌

✅ Correct Answer: (c) Half revolution

📌 Explanation:

In an AC generator, the current reverses direction after every half rotation.
This happens because, after half a turn, the coil’s arms switch positions, reversing the induced current direction.

📌 Domestic Electric Circuits – Detailed Notes

⚡ What is a Domestic Electric Circuit?

Electric power supply to homes is provided through the main supply (mains).
It is delivered either through overhead poles or underground cables.
The mains connection consists of:
✅ Live Wire (Red) – Positive terminal
✅ Neutral Wire (Black) – Negative terminal
✅ Earth Wire (Green) – Safety wire
The potential difference between the live and neutral wires in India is 220V.

🛠️ Components of a Domestic Electric Circuit

1️⃣ Electricity Meter

Measures electricity consumption in kilowatt-hours (kWh).

2️⃣ Main Fuse

Protects against overloading and short circuits.

3️⃣ Main Switch

Controls the entire power supply to the house.

4️⃣ Separate Circuits

15A Circuit: For high-power appliances (geysers, air coolers).
5A Circuit: For low-power appliances (lights, fans).

5️⃣ Parallel Wiring

Appliances are connected in parallel to ensure:
✅ Same voltage (220V) across all appliances.
✅ Independent functioning of each appliance.

6️⃣ Earth Wire (Green Insulation)

Connected to a metal plate deep in the ground.
Prevents electric shocks by providing a low-resistance path for leakage currents.

⚡ Safety Devices: Electric Fuse

Prevents damage due to short-circuiting and overloading.
Made of a low-melting point material (e.g., tin-lead alloy).
Melts when excessive current flows, breaking the circuit.

📌 Causes of Overloading & Short-Circuiting:
✅ Too many appliances connected to a single socket.
✅ Insulation damage causing a short circuit.
✅ Voltage surge from the supply.

⚙️ Applications of Domestic Circuits

✅ Home Power Supply – Provides safe electricity distribution.
✅ Parallel Connections – Ensure uninterrupted operation of appliances.
✅ Earthing – Prevents shocks and appliance damage.
✅ Fuse & MCB (Miniature Circuit Breaker) – Prevents fire hazards.

🎯 Key Takeaways

✔ Homes receive power through a live wire, neutral wire, and earth wire.
✔ Parallel wiring ensures equal voltage across appliances.
✔ Fuses protect against short-circuits and overloading.
✔ Earthing prevents electric shocks.

❓ Q U E S T I O N S & A N S W E R S

🧲 1. Name two safety measures commonly used in electric circuits and appliances.

✅ Answer:
📌 Two safety measures in electric circuits and appliances:
1️⃣ Electric Fuse – Protects the circuit from overloading and short circuits by melting and breaking the circuit if the current exceeds the safe limit.
2️⃣ Earthing (Grounding) – Provides a low-resistance path for leakage currents, preventing electric shocks and appliance damage.

🧲 2. An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.

✅ Answer:
📌 Given data:

Power of oven (P) = 2 kW = 2000 W
Voltage (V) = 220 V
Current rating of the circuit = 5 A

📌 Step 1: Calculate the required current using Ohm’s Law

$P = V \times I$ $I = \frac{P}{V} = \frac{2000}{220} = 9.09 A$

📌 Step 2: Compare with circuit’s current rating

The circuit allows only 5 A, but the oven requires 9.09 A.
Since the current exceeds the circuit limit, it will cause overloading.

📌 Expected Result:

The fuse will melt, or the circuit breaker will trip, cutting off the power supply.
This prevents fire hazards and damage to appliances.

🧲 3. What precaution should be taken to avoid the overloading of domestic electric circuits?

✅ Answer:
📌 Precautions to prevent overloading:
✔ Avoid plugging too many high-power appliances (like AC, heater, oven) into a single socket.
✔ Use separate circuits for high-power and low-power appliances.
✔ Ensure proper fuse or MCB (Miniature Circuit Breaker) installation to cut off excessive current.
✔ Use standard wires with proper insulation to prevent overheating and short-circuits.

🚀 Conclusion: Following these precautions ensures safe and efficient power distribution in homes. 🔬⚡

📌 E X E R C I S E S – Q U E S T I O N S & A N S W E R S

1. Which of the following correctly describes the magnetic field near a long straight wire?

(a) The field consists of straight lines perpendicular to the wire.
(b) The field consists of straight lines parallel to the wire.
(c) The field consists of radial lines originating from the wire.
(d) The field consists of concentric circles centred on the wire.

✅ Answer: (d) The field consists of concentric circles centred on the wire.

📌 Explanation:

The magnetic field around a straight current-carrying wire forms concentric circles around the wire.
This can be observed by sprinkling iron filings or using a compass around the wire.

2. The phenomenon of electromagnetic induction is

(a) The process of charging a body.
(b) The process of generating a magnetic field due to a current passing through a coil.
(c) Producing induced current in a coil due to relative motion between a magnet and the coil.
(d) The process of rotating a coil of an electric motor.

✅ Answer: (c) Producing induced current in a coil due to relative motion between a magnet and the coil.

📌 Explanation:

Electromagnetic induction is the process of inducing current in a coil by changing the magnetic field around it (discovered by Michael Faraday).

3. The device used for producing electric current is called a

(a) Generator
(b) Galvanometer
(c) Ammeter
(d) Motor

✅ Answer: (a) Generator.

📌 Explanation:

A generator converts mechanical energy into electrical energy using electromagnetic induction.

4. The essential difference between an AC generator and a DC generator is that

(a) AC generator has an electromagnet while a DC generator has a permanent magnet.
(b) DC generator will generate a higher voltage.
(c) AC generator will generate a higher voltage.
(d) AC generator has slip rings while the DC generator has a commutator.

✅ Answer: (d) AC generator has slip rings while the DC generator has a commutator.

📌 Explanation:

AC Generator: Uses slip rings, allowing current to alternate direction.
DC Generator: Uses a split-ring commutator, ensuring unidirectional current flow.

5. At the time of short circuit, the current in the circuit

(a) Reduces substantially.
(b) Does not change.
(c) Increases heavily.
(d) Varies continuously.

✅ Answer: (c) Increases heavily.

📌 Explanation:

A short circuit occurs when the live and neutral wires directly touch.
This results in a sudden increase in current, causing overheating or fire hazards.

6. State whether the following statements are true or false.

(a) An electric motor converts mechanical energy into electrical energy.
❌ False – An electric motor converts electrical energy into mechanical energy.

(b) An electric generator works on the principle of electromagnetic induction.
✅ True – A generator produces electricity by rotating a coil in a magnetic field.

(c) The field at the centre of a long circular coil carrying current will be parallel straight lines.
✅ True – The magnetic field inside a solenoid is uniform and parallel.

(d) A wire with green insulation is usually the live wire of an electric supply.
❌ False – The green wire is the earth wire, while the live wire is red.

7. List two methods of producing magnetic fields.

✅ Answer:
1️⃣ Using a Current-Carrying Conductor – A straight wire or coil carrying electric current produces a magnetic field around it.
2️⃣ Using a Permanent Magnet – A bar magnet or electromagnet generates a magnetic field in its surroundings.

8. How does a solenoid behave like a magnet? Can you determine the north and south poles of a current–carrying solenoid with the help of a bar magnet? Explain.

✅ Answer:
📌 Solenoid as a Magnet:

A solenoid (a coil of wire) carrying current produces a strong magnetic field similar to a bar magnet.
One end behaves as the north pole, and the other end behaves as the south pole.

📌 Determining Poles:

Bring the north pole of a bar magnet near one end of the solenoid.
If it repels, that end is also a north pole.
If it attracts, that end is a south pole.

9. When is the force experienced by a current–carrying conductor placed in a magnetic field largest?

✅ Answer:
📌 The force is maximum when the conductor is perpendicular to the magnetic field (at 90°).
📌 If the conductor is parallel to the magnetic field, no force is experienced.

10. Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of the magnetic field?

✅ Answer:
📌 Using Fleming’s Left-Hand Rule:
✔ Current flows opposite to electron motion (from front wall to back wall).
✔ The force on electrons is towards the right.
✔ The magnetic field must be downward.

✅ Conclusion: The magnetic field is directed downward.

11. Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor?

✅ Answer:
📌 Principle:

An electric motor works on the principle that a current-carrying conductor experiences a force in a magnetic field.

📌 Working:
✔ The current flows through the coil.
✔ Using Fleming’s Left-Hand Rule, one side of the coil is pushed up, and the other is pushed down.
✔ The split ring commutator reverses current every half rotation, ensuring continuous rotation.

📌 Function of Split Ring:

Reverses the direction of current every half-turn.
Ensures continuous rotation in the same direction.

12. Name some devices in which electric motors are used.

✅ Answer:
✔ Fans
✔ Refrigerators
✔ Washing Machines
✔ Water Pumps
✔ Electric Vehicles

13. A coil of insulated copper wire is connected to a galvanometer. What will happen if:

(i) A bar magnet is pushed into the coil?
✅ The galvanometer needle deflects, indicating an induced current.

(ii) The magnet is withdrawn?
✅ The needle deflects in the opposite direction, showing current reversal.

(iii) The magnet is held stationary inside the coil?
✅ No deflection, as no current is induced.

14. Two circular coils A and B are placed close to each other. If the current in coil A is changed, will some current be induced in coil B? Give reason.

✅ Answer:
✔ Yes, a current is induced in coil B.
✔ This happens due to electromagnetic induction, as the changing current in coil A creates a changing magnetic field, which induces current in coil B.

15. State the rule to determine the direction of:

(i) Magnetic field around a straight current-carrying conductor → Right-Hand Thumb Rule.
(ii) Force experienced by a current-carrying conductor → Fleming’s Left-Hand Rule.
(iii) Induced current in a rotating coil → Fleming’s Right-Hand Rule.

16. Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?

✅ Answer:

📌 Principle of an Electric Generator:

An electric generator works on the principle of electromagnetic induction.
When a coil rotates in a magnetic field, the magnetic flux linked with the coil changes, inducing a current in the circuit.
The direction of the induced current is given by Fleming’s Right-Hand Rule.

📌 Working of an Electric Generator:
✔ A rectangular coil (ABCD) is placed between the poles of a permanent magnet.
✔ The coil is attached to two slip rings (AC generator) or a split-ring commutator (DC generator).
✔ When the coil rotates, the magnetic flux linked with it changes, inducing an electric current.
✔ After every half rotation, the current reverses direction in an AC generator but remains the same in a DC generator.

📌 Function of Brushes:

Stationary brushes maintain contact with the rotating rings.
They transfer the induced current from the rotating coil to the external circuit.

17. When does an electric short circuit occur?

✅ Answer:
📌 A short circuit occurs when the live wire and the neutral wire come into direct contact due to:
✔ Faulty insulation of wires.
✔ Loose or damaged wiring.
✔ Overloaded circuits leading to overheating.

📌 Effects of Short Circuit:

A huge amount of current flows suddenly, causing overheating, sparks, or fire hazards.
Fuses and MCBs (Miniature Circuit Breakers) trip to prevent damage.

18. What is the function of an earth wire? Why is it necessary to earth metallic appliances?

✅ Answer:
📌 Function of an Earth Wire:

The earth wire (green insulation) provides a low-resistance path for leakage current.
Prevents electric shocks by keeping the metallic body of appliances at zero potential.

📌 Why is Earthing Necessary?
✔ If the live wire accidentally touches the metal body of an appliance, it could cause electric shocks.
✔ Earthing directs excess current safely into the ground, protecting users from electrical hazards.

Chapter 13: Magnetic Effects of Electric Current

⚡ The Magnetic Effect of Electric Current – An Introduction

📌 Magnetic Effect of Electric Current – Detailed Notes

🔋 Introduction

🧪 Activity 13.1: Demonstrating the Magnetic Effect of Electric Current

Materials Required:

Procedure:

Observation:

Conclusion:

🧲 Understanding Electromagnetism

👨‍🔬 Hans Christian Oersted and His Contribution to Electromagnetism

⚙️ Applications of the Magnetic Effect of Electric Current

🎯 Conclusion

📌 Magnetic Field and Field Lines – Detailed Notes

🧲 Introduction to Magnetic Field

🧪 Activity 13.2: Observing Magnetic Field Lines Using Iron Filings

Materials Required:

Procedure:

Observation:

Conclusion:

🧭 Activity 13.3: Drawing Magnetic Field Lines Using a Compass

Materials Required:

Procedure:

Observation:

Conclusion:

🔍 Properties of Magnetic Field Lines

⚙️ Applications of Magnetic Field Lines

🎯 Key Takeaways

❓ Q U E S T I O N & A N S W E R

📌 Magnetic Field Due to a Current-Carrying Conductor – Detailed Notes

🧲 Introduction

🔍 13.2.1 Magnetic Field Due to a Current Through a Straight Conductor

Key Observations

🧪 Activity 13.4: Observing Magnetic Field Using a Compass

Materials Required:

Procedure:

Observation:

Conclusion:

🧪 Activity 13.5: Visualizing Magnetic Field Lines Using Iron Filings

Materials Required:

Procedure:

Observation:

Conclusion:

🧭 Key Properties of Magnetic Field Around a Straight Conductor

✋ 13.2.2 Right-Hand Thumb Rule

Definition:

Rule Explanation:

Key Observations:

Significance of the Right-Hand Thumb Rule:

⚙️ Applications of Magnetic Field Due to a Current-Carrying Conductor

🎯 Key Takeaways

📌 Example 13.1: Direction of Magnetic Field Around a Power Line

✅ Solution:

🔄 Magnetic Field Direction:

❓ Q U E S T I O N S & A N S W E R S

📌 Magnetic Field Due to a Current Through a Circular Loop – Detailed Notes

🧲 Introduction

🔍 Key Observations

🧪 Activity 13.6: Observing Magnetic Field Due to a Circular Coil

Materials Required:

Procedure:

Observation:

✋ Right-Hand Thumb Rule for a Circular Loop

📌 Key Properties of the Magnetic Field in a Circular Loop

⚙️ Applications of Magnetic Fields in Circular Loops

🎯 Key Takeaways

📌 Magnetic Field Due to a Current in a Solenoid – Detailed Notes

🧲 What is a Solenoid?

🔍 Key Observations

✋ Right-Hand Thumb Rule for a Solenoid

🧪 Magnetization Using a Solenoid (Electromagnet Formation)

⚙️ Applications of Solenoids and Electromagnets

🎯 Key Takeaways

❓ Q U E S T I O N S & A N S W E R S

❓ Q U E S T I O N S & A N S W E R S

📌 Force on a Current-Carrying Conductor in a Magnetic Field – Detailed Notes

🧲 Introduction

🧪 Activity 13.7: Observing Force on a Current-Carrying Conductor

Materials Required:

Procedure: