Physics
In which of the following cases e.m.f. is induced?
(i) A current is started in a wire held near a loop of wire.
(ii) The current is switched off in a wire held near a loop of wire.
(iii) A magnet is moved through a loop of wire.
(iv) A loop of wire is held near a magnet.
Electro-Magnetism
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Answer
(i) Yes, e.m.f. is induced because when current is started in a wire held near a loop of wire, magnetic field varies due to which e.m.f. is induced.
(ii) Yes, e.m.f. is induced because when current is switched off in a wire held near a loop of wire, the current stops and magnetic field again varies and hence e.m.f. is induced.
(iii) Yes, e.m.f. is induced. When there is a relative motion between the magnet and a loop of wire, magnetic flux changes and e.m.f. is induced.
(iv) No, e.m.f. is not induced. When a loop of wire is held near a magnet, there is no change in magnetic field hence e.m.f. is not induced.
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