Page 125 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

C. State whether the following statements are true (T) or false (F).

1. An electric bell has an electromagnet.
2. A circuit diagram uses standard symbols for electric components.
3. When current is switched OFF in a room heater, it gives out heat.

4. A fuse wire is always connected to a live wire.
5. Hans Christian Oersted discovered tungsten.
6. A group of battery is called as a cell.

7. The polarity of an electromagnet can be reversed by changing the polarity ofthe
battery.

Ans: 1. (T) 2. (T) 3. (F) 4. (T) 5. (F) 6. (F) 7. (T)
D. Very short-answer questions.
1. Define overloading.

Ans: Overloading happens when too many electrical devices are connected to a single
circuit, causing it to draw more current than it can safely handle. This can lead to

overheating & potentially cause a fire.
2. State one advantage of an MCB.
Ans: MCB need not be replaced everytime excess current flows through it. It automatically

trips off and could be used when reset.
3. Draw symbols of switch in both ‘ON’ and ‘OFF’ positions.

Ans:

ON Position OFF Position

4. What is the filament of a bulb made up of?
Ans: The filament of a bulb is made of tungsten.

5. Which property of a conducting wire is used in an electric fuse?
Ans: The property of a conducting wire used in a electric fuse is its low melting point.
6. What is the full form of CFL and LED?
Ans: CFL - Compact Fluorescent Lamp

LED - Light Emitting Diode.
7. Define resistance.
Ans: Resistance is the opposition to the flow of electric current in any substance.

8. How can the strength of the electromagnet be changed?
Ans: The strength of an electromagnet can be changed by changing the strength of current
through the wire or by changing the number of turns in the coil.
E. Short-answer questions

1. Define a short circuit.
Ans: Short circuit is a problem in an electrical circuit when two or more wires, touch each

other. This may happen due to the wear and tear of insulation wires. If wires touch,

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