Page 126 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

it can result in the flow of very high current through the circuit. This high current can

destroy devices, melt the protective coating and also start a fire.
2. For a bulb to glow, it must be connected to a cell or a battery. Why?

Ans: It is because a cell or a battery provides the electric energy needed for the bulb
filament to get heated up and glow, so as to produce light.

3. Draw the symbol for the following.
(a) Bulb (b) Battery (c) Cell

Ans:
(a) (b) (c)

4. Differentiate between close circuit and open circuit.

Ans: (a) Open circuit: When there is a break in the continuous path of current, the circuit
is said to be open. When a circuit is open, the flow of current in the circuit stops.

(b) Closed circuit: When there is no break in the continuous path of current, the

circuit is said to be closed. When a circuit is closed, current continuously flows
in the circuit.

5. Why is an electric fuse required in all electrical appliances?
Ans: The electrical wires and appliances in our houses or buildings have a limit on the

maximum current that can flow through them. When the current exceeds this limit, it
can damage the electrical appliances or result in a fire. This stops the flow of current

through the circuit and protects the wires and appliances from being damaged.

6. Why are compact fluorescent lamps (CFLs) preferred over electric bulbs?
Ans: Electric bulbs (also known as incandescent lamps) consume a lot of electricity. So,

they are being replaced by compact fluorescent lamps or CFLs and light-emitting
diodes or LEDs, which are more energy-efficient. These devices do not work on the

heating effect of current.
7. Explain the function of a cell in an electric circuit.

Ans: An electric cell is a common source of electric current to operate devices, such as a
torch, radio, clock, remote control etc. It produces electric current with the help of

the chemicals stored in it.
8. Write a short note on the heating effect of electric current.

Ans: Heating effect of electric current

The heating effect of electric current occurs when current flows through a conductor,
causing it to heat up due to resistance. This effect is used in devices like heater, iron

& toasters.

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