CBSE Class 10 Science 2018 · Paper 31(B) · Question 14

Activity: (i) Take a coil of insulated copper wire having a large number of turns and connect its two ends to a galvanometer. (ii) Take a strong bar magnet and move its north pole towards one end of the coil. The galvanometer needle deflects momentarily, say to the right, showing that a current flows in the coil. (iii) Hold the magnet still near the coil: the deflection drops to zero. (iv) Pull the north pole away from the coil: the needle deflects to the left, showing a current in the opposite direction. (v) Keep the magnet fixed and move the coil towards it or away from it: the needle deflects in the same way, and when the coil is stationary with respect to the magnet the deflection drops to zero. Conclusion: a current is induced in the coil only while the magnetic field around it is changing, that is, while the magnet and the coil move relative to each other.