# Magnetic Effects of Electric Current | Activities in Text Book with Solution

Activity 13.8

Take a coil of wire AB having a large number of turns.

Connect the ends of the coil to a galvanometer as shown in Fig. 13.16.

 Fig. 13.16

Take a strong bar magnet and move its north pole towards the end B of the coil. Do you find any change in the galvanometer needle?

There is a momentary deflection in the needle of the galvanometer, say to the right. This indicates
the presence of a current in the coil AB. The deflection becomes zero the moment the motion of the magnet stops.

Now withdraw the north pole of the magnet away from the coil. Now the galvanometer is deflected toward the left, showing that the current is now set up in the direction opposite to the first.

Place the magnet stationary at a point near to the coil, keeping its north pole towards the end B of the coil. We see that the galvanometer needle deflects toward the right when the coil is moved towards the north pole of the magnet. Similarly the needle moves toward left when the coil is moved away.

When the coil is kept stationary with respect to the magnet, the deflection of the galvanometer drops to zero. What do you conclude from this activity?

✅ Answer: If the south pole of the magnet is moved towards the end B, the deflections in the galvanometer would just be opposite to the previous case. When the coil & magnet are stationary, there is no deflection in the galvanometer.

Thus, this activity shows that the motion of a magnet with respect to the coil produces an induced potential difference, which sets up an induced electric current in the circuit.