Question

A metallic block carrying current i is subjected to a uniform magnetic induction B as shown in the figure. The moving charges experience a force F given by ……. which results in the lowering of the potential of the face ……. Assume the speed of the carriers to be $\mathcal { V }$

• A.
• B.
• C.
• D.

Answer 1

Answer: (C)

Answer 2

As the block is of metal, the charge carriers are electrons; so for current along positive x-axis, the electrons are moving along negative x-axis, i.e. $\vec { v } = - v i$

and as the magnetic field is along the y-axis, i.e.

so $\vec { F } = q ( \vec { v } \times \vec { B } )$ for this case yield

i.e.,$\vec { F } = e v B \hat { k }$ [As $\hat { i } \times \hat { j } = \hat { k }$]

As force on electrons is towards the face ABCD, the electrons will accumulate on it an hence it will acquire lower potential.