Page 128 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

the two ends of the wire wound around the nail. Place some paper clips near the

nail. Switch on the circuit and observe the paper clips.
You will see that when electric current passes through the coil, the coil behaves like a

magnet and the paper clips cling to it, as shown in Fig. (a). When current is switched
off, the coil loses its magnetism and paper clips fall off, as shown in Fig. (b). Such
a coil that behaves like a magnet as long as there is current passing through it, is

called an electromagnet. The electromagnet loses its magnetism when the current is
switched off.
4. Can we use the same fuse in a geyser and a television set? Explain.

Ans: No we cannot use the same fuse in a geyser & a television set because they have
different power requirements. A geyser requires a higher current fuse due to its
higher power consumption, while a television needs a lower current fuse. Using the

wrong fuse can either cause the fuse to blow unnecessarily or fail to protect the
device properly.

5. Describe the magnetic effect of current with the help of an activity.
Ans: Aim: To demonstrate the magnetic effect of electric current.
Principle: When electric current passes through a

wire or a conductor, it generates a magnetic field in
the surrounding area. This magnetism deflects the

magnetic needle from its usual north-south direction
indicating magnetic effect.
Material required: Compass needle, connecting wire,

discarded matchbox, an electric wire, cell, switch and
bulb
Procedure:

 Take the cardboard tray of an empty matchbox and wrap around an electric
wire a few times around it.

 Now place a compass needle inside the cardboard tray.
 Connect the free ends of the wire to a cell and a bulb through a switch using
connecting wires as shown.

 Observe the compass needle carefully. Now, turn the switch ‘ON’ and observe
again.

 Turn the switch ‘OFF’ position and observe. What do you see?
Observation: You will find that the compass needle shows deflection as long as the
electric current passes through the wire wound around the cardboard tray. This

happens because the electric current produces a magnetic field that influences the
compass needle to deflect.

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