Extra 20 important long-answer questions from the chapter:12 "Magnetic Effects of Electric Current" for Class 10 CBSE Science:
1. What are magnetic field lines? List the properties of magnetic field lines.
Ans:
Magnetic field lines are imaginary lines that represent the direction and strength of the magnetic field around a magnet.
Properties:
Magnetic field lines always
form
closed loops.
They originate from the
north pole
and end at the
south pole
outside the magnet.
Inside the magnet, they move from the
south pole to the north pole
.
The closer the field lines, the stronger the magnetic field.
No two magnetic field lines intersect.
2. Describe an experiment to show that a current-carrying conductor produces a magnetic field.
Ans:
Aim: To show that a current-carrying conductor produces a magnetic field.
Materials: A battery, a straight wire, a switch, and a compass.
Procedure:
Connect the wire to the battery and switch.
Place the compass near the wire and note its direction.
Switch on the current and observe the compass needle.
Reverse the current direction and note the needle’s movement.
Observation: The compass needle deflects when current flows, proving that a magnetic field is produced.
Conclusion: A current-carrying conductor generates a magnetic field around it.
3. What is the Right-Hand Thumb Rule? Explain its application with a diagram.
Ans:
Right-Hand Thumb Rule: If we point the thumb of the right hand in the direction of the current, then the curled fingers show the direction of the magnetic field.
Application:
Used to determine the direction of the magnetic field in a straight conductor and solenoid.
Helps understand electromagnetism in electric motors and generators.
4. Explain the magnetic field due to a current-carrying circular loop.
Ans:
A
current-carrying circular loop
produces a
magnetic field
similar to a bar magnet.
The field is
concentric circles
near the wire.
At the
centre
of the loop, the field lines are
straight and parallel
, meaning the field is strong.
The
Right-Hand Thumb Rule
helps find the
field direction
at any point.
Increasing the
current
or the
number of loops
strengthens the field.
5. What is a solenoid? Describe the magnetic field inside a solenoid.
Ans:
A solenoid is a coil of insulated wire wound in a cylindrical shape. When current flows through it, a strong magnetic field is created inside the coil.
Magnetic Field of a Solenoid:
Inside the solenoid, the field is
uniform and strong
, resembling a bar magnet.
One end behaves as the
north pole
, and the other as the
south pole
.
The strength of the field depends on:
The
number of turns
in the coil.
The
current flowing
through the coil.
The
core material
inside the solenoid (e.g., iron increases the field strength).
6. Explain the working principle of an electric motor with a diagram.
Ans:
An electric motor converts electrical energy into mechanical energy based on Fleming’s Left-Hand Rule.
Working Principle: A current-carrying coil placed in a magnetic field experiences a force, causing rotation.
Diagram:
(Insert a labelled diagram of an electric motor.)
Working:
When current flows, forces act on the coil’s two arms in opposite directions.
The coil rotates, and the
split ring commutator
ensures continuous rotation.
The motor keeps running as long as current flows.
7. State and explain Fleming’s Left-Hand Rule.
Ans:
Fleming’s Left-Hand Rule: If the thumb, forefinger, and middle finger of the left hand are stretched mutually perpendicular to each other:
Forefinger:
Points in the direction of the
magnetic field
.
Middle finger:
Points in the direction of
current
.
Thumb:
Points in the direction of
force (motion)
.
Application: Used in electric motors to determine the direction of rotation.
8. What is electromagnetic induction? Explain Faraday’s experiment.
Ans:
Electromagnetic induction is the phenomenon where a changing magnetic field induces a current in a conductor.
Faraday’s Experiment:
A coil is connected to a galvanometer.
A bar magnet is moved towards and away from the coil.
The galvanometer shows deflection, indicating induced current.
Faster movement induces a stronger current.
Conclusion: A changing magnetic field induces an electric current.
9. State and explain Fleming’s Right-Hand Rule.
Ans:
Fleming’s Right-Hand Rule: If the thumb, forefinger, and middle finger of the right hand are stretched mutually perpendicular to each other:
Forefinger:
Points in the direction of
magnetic field
.
Thumb:
Points in the direction of
motion
.
Middle finger:
Points in the direction of
induced current
.
Application: Used in electric generators to determine the direction of induced current.
10. Explain the working of an AC generator.
Ans:
An AC generator converts mechanical energy into electrical energy based on electromagnetic induction.
Working:
A coil rotates in a magnetic field, inducing an alternating current.
Slip rings allow the current to change direction periodically.
11. What is an electric generator? How does it work?
Ans:
An electric generator converts mechanical energy into electrical energy using electromagnetic induction.
A
coil
rotates in a magnetic field.
The changing magnetic field induces
current
in the coil.
Slip rings (AC generator) or a commutator (DC generator) complete the circuit.
12. What is earthing? Why is it important in household circuits?
Ans:
Earthing is a safety measure where excess current is directed into the ground.
Prevents
electric shocks
.
Protects appliances from
overheating
.
13. What is overloading and short-circuiting? How can they be prevented?
Ans:
Overloading:
Too many devices connected to a circuit, causing excess current.
Short-Circuiting:
Live and neutral wires touch, causing a surge of current.
Prevention:
Use fuses, circuit breakers, and avoid excess loads.
14. What is a fuse? How does it work?
Ans:
A fuse is a safety device that melts when excess current flows, breaking the circuit and preventing damage.
15. Why is AC used in household circuits instead of DC?
Ans:
AC voltage can be easily
stepped up/down
using transformers.
It can be transmitted
over long distances
with minimal loss.
