Question

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.

Answer 1

• 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