Question

Induced emf can be produced by:

• A. a moving magnet.
• B. a steady current carrying moving wire.
• C. an alternating current carrying wire at rest.
• D. a steady current carrying wire at rest.

Answer 1

Answer: (A), (B), (C)

The correct options are
A a moving magnet.
B a steady current carrying moving wire.
C an alternating current carrying wire at rest.

From the Faraday's law of electromagnetic induction, we know that a varying magnetic field can produce induced emf in a coil. Varying magnetic field can be produced by a moving magnet. Also we know that a current carrying wire produces magnetic field. If the current through it changes then the magnetic field associated with the coil changes with time. Then it can produce an emf in the coil. If current is fixed, then the magnetic field will be fixed. It cannot produce induced emf in the coil. But if we move the wire then at any point, the magnetic field will be changed. Then it can produce emf in the coil.