Question

Assertion: The energy of a charged particle moving at right angles to a uniform magnetic field does not change.
Reason: No work is dome by the magnetic field on the charged particle.
State whether
1. Both A and R are true, R is correct explanation.
2. Both A and R are true, R is not the correct explanation of A.
3. A is true R is false
4. A is false R is true.​

Answer 1

1)Both a and b are true and B is the correct explanation of A

Answer 2

Both Assertion and reason are false.

Option (4) is correct.

Explanation:

Both Assertion and reason are false.

The reason is that the force on a charged particle moving in a uniform magnetic field always acts in direction which is perpendicular to the direction of motion of the charge.

If work done by magnetic field on the charge is zero, [W = FS cosθ],  then the energy of the charged particle does not change.