Magnetic Effect Of Electric Current

MAGNTIC EFFECT OF ELECTRIC CURRENT

Activity 14.5

Take the cardboard tray from inside a discarded matchbox. Wrap an electric wire a few times around the cardboard tray. Place a small compass needle inside it. Now connect the free ends of this wire to an electric cell through a switch as shown in Fig.14.17.

Note the direction in which the compass needle is pointing. Bring a bar magnet near the compass needle. Observe what happens. Now, while watching the compass needle carefully, move the switch to the ‘ON’ position.

Fig. 14.18 Hans Christian Oersted (A.D. 1777-1851)

What do you observe? Does the compass needle deflect? Move the switch back to the ‘OFF’ position. Does the compass needle come back to its initial position? Repeat the experiment a few times What does this experiment indicate?

We know that the needle of a compass is a tiny magnet, which points in north-south direction. When we bring a magnet close to it, the needle gets deflected. We have also seen that compass needle gets deflected when the current flows in a nearby wire. Can you connect the two observations? When the current flows through a wire, does the wire behave like a magnet?

This is what a scientist called Hans Christian Oersted (Fig. 14.18) also wondered. He was the first person who noticed the deflection of compass needle every time the current was passed through the wire.

So, when electric current passes through a wire, it behaves like a magnet. This is the magnetic effect of the electric current. In fact, an electric current can be used to make magnets. Do you find it too surprising? Let us try it out.

Fig. 14.19 An electromagnet