Magnetic Effects of Electric Current

1. What happens when a magnetic compass is brought near a current-carrying conductor?

The compass needle gets deflected, showing that an electric current produces a magnetic field.

2. What is the shape of the magnetic field lines around a straight current-carrying conductor?

They form concentric circles around the conductor.

3. How does the strength of the magnetic field around a straight conductor depend on current and distance?

• It increases with increase in current.

• It decreases as the distance from the conductor increases.

4. State the Right-Hand Thumb Rule.

If you hold the conductor in your right hand with the thumb pointing in the direction of current, then the curled fingers show the direction of magnetic field lines around the conductor.

5. What is the magnetic field inside a current-carrying solenoid?

The magnetic field inside a solenoid is strong, uniform, and straight (similar to that of a bar magnet).

6. What are the factors on which the magnetic field of a solenoid depends?

• Strength of current

• Number of turns per unit length

• Nature of core material (e.g., soft iron increases field)

7. What is an electromagnet?

An electromagnet is a temporary magnet made by winding a coil of wire around a soft iron core and passing current through it.

8. What is the difference between electromagnet and permanent magnet?

Electromagnet	Permanent Magnet
Temporary magnet	Permanent magnet
Strength can be changed	Strength fixed
Magnetic field produced by current	Magnetic field always present

9. What is the function of an electric fuse?

A fuse protects appliances from damage by breaking the circuit when excess current flows.

10. What is meant by short circuit?

Short circuit happens when live wire and neutral wire come into direct contact, causing a sudden increase in current.

11. What is overloading?

Overloading happens when too many appliances are connected to a single socket, causing excessive current flow.

12. What is the role of the Earth wire?

Earth wire protects users from electric shocks by providing a path for the leakage current to the ground.

13. What is the direction of force on a current-carrying conductor in a magnetic field?

The direction is given by the Fleming’s Left-Hand Rule.

14. State Fleming’s Left-Hand Rule.

Stretch the thumb, index finger, and middle finger of your left hand mutually perpendicular:

• Index finger → magnetic field

• Middle finger → current

• Thumb → direction of force

15. What is an electric motor?

An electric motor converts electrical energy into mechanical energy using the force on a current-carrying coil in a magnetic field.

16. What is electromagnetic induction?

Electromagnetic induction is the production of current in a coil due to change in magnetic field around it.

17. State Fleming’s Right-Hand Rule.

Thumb = direction of motion
Index finger = magnetic field
Middle finger = induced current

18. What is an AC generator?

A device that converts mechanical energy into electrical energy and produces alternating current (AC).

19. What is the difference between AC and DC?

• AC (Alternating Current): direction changes periodically.

• DC (Direct Current): flows in one direction only.

20. Why is AC preferred over DC for transmission?

AC can be easily stepped up or down using transformers, reducing power loss during long-distance transmission.