Question

Establish the fact that the relative motion between the coil and the magnet induces an emf in the coil of a closed circuit.

Answer 1

1. In first experiment when bar magnet is placed close to the coil, magnetic lines pass through coil, the magnetic flux in coil increases and emf is induced hence electric current flows in the circuit.
2. At the same time when they recede away from one another magnetic flux decreases emf is induced in opposite direction. Current flows in opposite direction. So there is a deflection in the galvanometer.
3. In the second experiment, when the primary circuit is open, no electric current flows in it, magnetic flux linked with the secondary coil is zero.
   
   (a) Right deflection
4. When primary circuit is closed, increasing current produces a magnetic field. So magnetic flux linked with coil increases. This induced current in the secondary coil.
   
   (a) Left deflection
   
5. When the primary circuit is broken, decreasing primary current induces a current in the secondary coil but in opposite direction. So there is a deflection in Galvanorneter.
   (a) 
   
   (b) 
   
   (c)