NEET Physics: Magnetic Effects of Current questions with solutions

Q1. Assertion (A): To protect any instrument from external magnetic field, it is put inside an iron box Reason (R) : Iron is a ferromagnetic substance

1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true and R is not correct explanation of
3. A is true, but R is false
4. A is false, but R is true

Answer: Both A and R are true and R is the correct explanation of A

Both statements are true: iron is ferromagnetic, so it has very high magnetic permeability. That makes an iron enclosure divert external magnetic field lines through itself, reducing the field inside and protecting the instrument.

Q2. Sensitivity of a moving coil galvanometer can be increased by Fill in the blank.

1. decreasing number of turns in rectangular coil
2. decreasing magnetic induction of magnetic field
3. increasing area of rectangular coil
4. increasing twist constant of phosphor bronze fiber

Answer: increasing area of rectangular coil

The deflection of a moving-coil galvanometer is proportional to the magnetic torque, which depends on the coil area. Increasing the area increases torque for the same current, so the instrument becomes more sensitive.

Q3. Assertion The sensitivity of a moving coil galvanometer is increased by placing a suitable magnetic material as a core inside the coil. Reason Soft iron has a high magnetic permeability and cannot be easily magnetized or demagnetized.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Assertion is incorrect but Reason is correct

Answer: Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

A soft iron core increases the magnetic field in the coil because it has very high magnetic permeability, so the galvanometer becomes more sensitive. The reason is correct and it explains why the sensitivity increases.

Q4. The temperature at which the domain structure gets destroyed and ferromagnetic substance is converted into paramagnetic substance is called as

1. Domain
2. Curie Temperature
3. Rowland
4. Magnetic Field Intensity

Answer: Curie Temperature

The domain structure in a ferromagnet breaks down at a specific critical temperature, causing the material to lose ferromagnetism and become paramagnetic. That temperature is called the Curie temperature.

Q5. Two straight parallel wires carrying current in the opposite directions repe each other, because of

1. Electrical force between them
2. Magnetic force between them
3. Gravitational force between them
4. Nuclear force between them

Answer: Magnetic force between them

Each wire produces a magnetic field that acts on the moving charges in the other wire. For opposite current directions, the magnetic interaction is repulsive, so the wires push apart due to magnetic force.

Q6. Assertion A current carrying conductor experiences a force in a magnetic field. Reason The net charge on a current carrying conductor is zero.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Assertion is incorrect but Reason is correct

Answer: Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

The assertion is true because a current-carrying conductor in a magnetic field experiences a force due to the motion of its charges. The reason is also true, but zero net charge does not explain the force; the force arises from the moving charges inside the conductor.