Course Content
Class 7th Science
0/36
Class 7th Math
0/71
Class 7 Social Science Geography
0/20
Class 7 Social Science History
0/20
Class 7 Social Science Civics
0/19
Class 7 English Honeycomb
0/20
Class 7 English Honeycomb Poem
0/18
Class 7 English An Alien Hand Supplementary
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Online Class For 7th Standard Students (CBSE)

Question 1.
Draw in your notebook the symbols to represent the following components of electrical circuits : connecting wires, switch in the ‘OFF’ position, bulb, cell, switch in the ‘ON’ position and battery.
Solution:

Question 2.
Draw the circuit diagram to represent the circuit shown

Question 4.
The bulb in the circuit shown does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.

Question 5.
Name any two effects of electric current.
Solution:

1. Heating effect
2. Magnetic effect.

Question 6.
When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.
Solution:
We know that the needle of a compass is itself a tiny magnet, which points in a north-south direction. When we bring a magnet close to it, the needle gets deflected. When an electric current passes through a wire it also behaves like a magnet. And hence the needle of the compass will also be deflected.

Question 7.
Will the compass needle show deflection when the switch in the circuit shown by is closed?

2. The combination of two or more cells is called a ………..

3.When current is switched ‘on’ in a room heater, it ………..

4. The safety device based on the heating effect of electric current is called a ………..

Solution:

1. positive
2. battery
3. get heated
4. fuse

Question 9.
Mark ‘T’ if the statement is True and ‘F’ if it is False:

1. To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell. (T/F)
2. When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. (T/F)
3. An electromagnet does not attract a piece of iron. (T/F)
4. An electric bell has an electromagnet. (T/F)

Solution:

1. F
2. T
3. F
4. T

Question 10.
Do you think an electromagnet can be used for separating plastic bags from a garbage heap?
Solution:
No. An electromagnet develops magnetic property and it will attract only the magnetic substances. Since the plastic bags are non-magnetic so they cannot be separated from a garbage heap by an electromagnet.

Question 11.
An electrician is carrying out some repairs in your house. He wants to replace a fuse with a piece of wire. Would you agree? Give reasons for your response.
Solution:
No, I will not agree. An electric fuse is made from some special material which blows off when the current exceeds the safe limit, while an ordinary wire may not perform this function and will cause damages to electrical circuits and appliances and also can cause fires. Hence I will insist to use proper fuse wire carrying the ISI mark.

Question 12.
Zubeda made an electric circuit using a cell holder shown, a switch, and a bulb. ‘When she put the switch in the ‘ON’ position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.
Solution:
These may be the reasons by which the bulb will not glow.

• The cell may be connected in an improper way. Check out that the positive terminal of one cell is connected to the negative terminal of the other or not.
• The junctions of the wire may be loose. Check them again.
• Check the condition of the bulb. Replace it. if it is fused.

Question 13.
In the circuit shown

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