Extra 30 short answer questions from the chapter:12 "Magnetic Effects of Electric Current" for Class 10 CBSE Science:
What is a magnetic field? How can it be represented?
Ans:
A magnetic field is the region around a magnet where its influence can be felt. It is represented using magnetic field lines, which show the direction and strength of the field.
State the Right-Hand Thumb Rule.
Ans:
According to the Right-Hand Thumb Rule, if the thumb of the
right hand
points in the direction of current, then the fingers wrapped around the conductor show the direction of the magnetic field.
Why do magnetic field lines never intersect each other?
Ans:
Magnetic field lines never intersect because at the point of intersection, the compass needle would point in two different directions, which is not possible.
Describe the pattern of magnetic field lines around a straight current-carrying conductor.
Ans:
The magnetic field lines around a straight current-carrying conductor form concentric circles perpendicular to the conductor, with their direction given by the Right-Hand Thumb Rule.
What is the shape of the magnetic field produced by a current-carrying circular loop?
Ans:
The magnetic field lines form concentric circles at every point around the loop. At the
centre
, the field lines appear almost straight and parallel, resembling the field of a bar magnet.
How does the strength of the magnetic field due to a straight conductor depend on current and distance?
Ans:
The strength of the magnetic field increases with an increase in current and decreases as the distance from the conductor increases.
What is a solenoid? What is the pattern of its magnetic field?
Ans:
A solenoid is a long coil of wire with many turns. The magnetic field inside a solenoid is strong and uniform, similar to that of a bar magnet, with distinct north and south poles.
What happens to the magnetic field inside a solenoid when the number of turns is increased?
Ans:
Increasing the number of turns in a solenoid strengthens the magnetic field because more turns mean more contributions to the total magnetic effect.
How can you increase the strength of an electromagnet?
Ans:
The strength of an electromagnet can be increased by:
Increasing the number of turns in the coil
Increasing the current in the coil
Using a soft iron core inside the coil
State the difference between a permanent magnet and an electromagnet.
Ans:
Permanent Magnet:
Retains its magnetism even when the external influence is removed.
Electromagnet:
Acts as a magnet only when current flows through it.
State Fleming’s Left-Hand Rule and its application.
Ans:
According to Fleming’s Left-Hand Rule, if the thumb, forefinger, and middle finger of the left hand are arranged mutually perpendicular, with:
Forefinger → Magnetic field direction
Middle finger → Current direction
Thumb → Force direction
This rule is used in electric motors.
What is an electric motor? What is its working principle?
Ans:
An electric motor is a device that converts electrical energy into mechanical energy. It works based on
Fleming’s Left-Hand Rule
, where a current-carrying conductor in a magnetic field experiences a force that causes rotation.
What is a commutator? What is its function in an electric motor?
Ans:
A commutator is a device that reverses the direction of current in an electric motor, ensuring continuous rotation in the same direction.
What happens if the direction of current in a motor is reversed?
Ans:
If the current direction is reversed, the direction of force on the conductor (as per Fleming’s Left-Hand Rule) also reverses, making the motor rotate in the opposite direction.
State the principle of electromagnetic induction.
Ans:
Electromagnetic induction is the phenomenon where a changing magnetic field induces an electric current in a conductor.
State Fleming’s Right-Hand Rule.
Ans:
According to Fleming’s Right-Hand Rule, if the thumb, forefinger, and middle finger of the right hand are held perpendicular to each other, with:
Forefinger → Magnetic field direction
Thumb → Motion of the conductor
Middle finger → Induced current direction
It is used in electric generators.
What is an electric generator? What is its working principle?
Ans:
An electric generator converts mechanical energy into electrical energy based on the principle of
electromagnetic induction
(Fleming’s Right-Hand Rule).
Differentiate between AC and DC generators.
Ans:
AC Generator:
Produces alternating current, uses slip rings.
DC Generator:
Produces direct current, uses a commutator.
What happens if a closed coil is moved in a uniform magnetic field?
Ans:
If a closed coil is moved perpendicular to a uniform magnetic field, no current is induced because the magnetic field remains unchanged.
How is electromagnetic induction used in power generation?
Ans:
In power plants, rotating turbines move conductors within magnetic fields, inducing current through electromagnetic induction, generating electricity.
What is earthing? Why is it important?
Ans:
Earthing connects electrical appliances to the ground, providing a safe path for leakage currents, preventing electric shocks.
What is a fuse? How does it work?
Ans:
A fuse is a safety device that melts when excessive current flows, breaking the circuit and preventing damage.
Why is the live wire dangerous?
Ans:
The live wire carries high voltage current and can cause electric shocks if touched.
What is the function of a circuit breaker?
Ans:
A circuit breaker automatically cuts off the current when a fault is detected, protecting the electrical system.
What are the differences between a fuse and a circuit breaker?
Ans:
Fuse:
Works once and needs replacement.
Circuit Breaker:
Can be reset and reused.
What is short-circuiting? How does it occur?
Ans:
Short-circuiting occurs when live and neutral wires come into direct contact, causing excessive current flow and heating.
What is overloading? How can it be prevented?
Ans:
Overloading happens when too many appliances are connected to a single circuit. It can be prevented by using proper fuses and circuit breakers.
Why do we use AC instead of DC in household circuits?
Ans:
AC is preferred because it is easy to generate, transmit over long distances with minimal loss, and can be stepped up/down using transformers.
What is the frequency of AC in India?
Ans:
The frequency of alternating current (AC) in India is
50 Hz
.
Why are household appliances connected in parallel?
Ans:
In a parallel circuit, each appliance gets the same voltage, and failure of one appliance does not affect the others.
