| ASSERTION: Free electrons always keep on moving in a conductor even then no magnetic force act on them in magnetic field unless a current is passed through it. |
| REASON: The average velocity of free electron is zero. |
A) If both assertion and reason are true and reason is the correct explanation of assertion.
B) If both assertion and reason are true and reason is not the correct explanation of assertion.
C) If assertion is true but reason is false.
D) If both assertion and reason are false.
E) If assertion is false but reason is true.
Correct Answer: A
Solution :
In an absence of the electric current, the free electrons in a conductor are in state of random motion, like molecule in a gas. Their average velocity is zero. i.e. they do not have any velocity in a direction. As a result, there is no net magnetic force on the free electrons in the magnetic field. On passing the current, the free electrons acquire drift velocity in a definite direction; hence magnetic force acts on them, unless the field has no perpendicular component.
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