Assertion (A): The energy of a charged particle moving in a magnetic field does not change.
Reason (R): It is because the work done by the magnetic force on the charge moving in a magnetic field is zero.
Reason (R): It is because the work done by the magnetic force on the charge moving in a magnetic field is zero.
- (A)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).✓ Correct
- (B)Both Assertion (A) and Reason (R) are true and Reason (R) is NOT the correct explanation of Assertion (A).
- (C)Assertion (A) is true but Reason (R) is false.
- (D)Assertion (A) is false and Reason (R) is also false.
Answer: (A)
Solution
The magnetic force is always perpendicular to the velocity, so it can do no work on the charge.
Zero work means the kinetic energy, and hence the total energy of the charged particle, stays constant - so Assertion (A) is true.
Reason (R) correctly states this zero-work fact, and it is exactly why the energy does not change, so (R) is the correct explanation of (A).
Zero work means the kinetic energy, and hence the total energy of the charged particle, stays constant - so Assertion (A) is true.
Reason (R) correctly states this zero-work fact, and it is exactly why the energy does not change, so (R) is the correct explanation of (A).
CBSE Class 12 Board · 2024 · Single correct option