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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.


  • 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

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