A rod AB moves with a uniform velocity v in a uniform magnetic field as shown in figure.
(a) The rod becomes electrically charged.
(b) The end A becomes positively charged.
(c) The end B becomes positively charged.
(d) The rod becomes hot because of Joule heating.

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Solution

(b) The end A becomes positively charged.

Due to electromagnetic induction, emf e is induced across the ends of the rod. This induced emf is given by
$e = B v l$
The direction of this induced emf is from A to B, that is, A is at the higher potential and B is at the lower potential. This is because the magnetic field exerts a force equal to $q v B$ on each free electron where q is $-$ 1.6 × 10^-16 C. The force is towards AB by Fleming's left-hand rule; hence, negatively charged electrons move towards the end B and get accumulated near it. So, a negative charge appears at B and a positive charge appears at A.

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A rod AB moves with a uniform velocity v in a uniform magnetic field as shown in figure. (a) The rod becomes electrically charged. (b) The end A becomes positively charged. (c) The end B becomes positively charged. (d) The rod becomes hot because of Joule heating.

A rod AB moves with a uniform velocity v in a uniform magnetic field as shown in figure.
(a) The rod becomes electrically charged.
(b) The end A becomes positively charged.
(c) The end B becomes positively charged.
(d) The rod becomes hot because of Joule heating.