# Explain the phenomenon of electromagnetic induction. Describe an

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Explain the phenomenon of electromagnetic induction. Describe an experiment to show that a current is set up in a closed loop when an external magnetic field passing through the loop increases or decreases.

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• Electromagnetic induction is a phenomenon of generation of an electric current in a closed circuit by changing the magnetic field.
• Electric current produced by this phenomenon is called as induced current and potential difference set in the circuit due to induced current is called induced emf.

Experiment:

• Take two different coils of copper wire having large number of turns (say 50 and 100 turns respectively).
• Insert them over a non-conducting cylindrical roll, as shown in Fig.
• (You may use a thick paper roll for this purpose.)
• Connect the coil-1, having larger number of turns, in series with a battery and a plug key. Also connect the other coil-2 with a galvanometer as shown.
• Plug in the key. Observe the galvanometer. Is there a deflection in its needle?
• You will observe that the needle of the galvanometer instantly jumps to one side and just as quickly returns to zero, indicating a momentary current in coil-2.
• Disconnect coil-1 from the battery.
• You will observe that the needle momentarily moves, but to the opposite side.
• It means that now the current flows in the opposite direction in coil-2