Before trying to answer the NCERT exercise questions, you should have a thorough understanding of class 7 Science chapter 10 i.e. ‘Electric Current and its Effects‘.
If you haven’t understood the chapter yet, then worry not you can go through it easily and develop a crystal clear understanding of various concepts from our notes whose link has been provided below. ⤵️
NCERT Exercise Questions & Answers
Que. 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
Ans. 1 The symbols of the following electric components are:
Que. 2 Draw the circuit diagram to represent the circuit shown in Fig.10.21.
Ans. 2 The circuit diagram for the circuit given in Fig 10.21 is
Que. 3 Fig.10.22 shows four cells fixed on a board. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells.
Ans. 3 The four cells that are given in Fig. 10.22 have to be connected this way to form a battery.
Que. 4 The bulb in the circuit shown in Fig.10.23 does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.
Ans. 4 The bulb in the circuit shown in Fig. 10.23 will not glow because the connections of the electric cells to form a battery are wrong and the bulb is connected to both the negative terminals of the electric cells. To rectify this mistake and make the bulb glow all we have to do is connect the cells correctly (the positive terminal of one cell connected to the negative terminal of the next cell) to form a battery and then connect one end of the bulb to the positive terminal of the battery and the other end of the bulb to the negative terminal of the battery.
Que. 5 Name any two effects of electric current.
Ans. 5 The two common effects of electric current are:
- The heating effect of the electric current.
- Magnetic effect of the electric current.
Que. 6 When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain
Ans. 6 The deflection of the compass needle from its north-south position, when it is kept near a current-carrying wire is due to the magnetic effect of the electric current. When electric current passes through a wire it behaves like a magnet and a compass needle is also a tiny magnet. And, as we know two magnets present nearby either attract or repel, hence the needle gets deflected from its original north-south position.
Que. 7 Will the compass needle show deflection when the switch in the circuit shown by Fig.10.24 is closed?
Ans. 7 No, the compass needle will not show any deflection even if the circuit is closed because there is no current source (cell or battery) that is connected to the circuit hence there will be no flow of current and no deflection of the compass needle.
Que. 8 Fill in the blanks:
(a) A longer line in the symbol for a cell represents its______________terminal.
(b) The combination of two or more cells is called a _____________.
(c) When current is switched ‘on’ in a room heater, it ________.
(d) The safety device based on the heating effect of electric current is called a ___________.
Ans. 8 (a) A longer line in the symbol for a cell represents its positive terminal.
(b) The combination of two or more cells is called a battery.
(c) When current is switched ‘on’ in a room heater, it produces heat.
(d) The safety device based on the heating effect of electric current is called an electric fuse.
Que. 9 Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) 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)
(b) When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. (T/F)
(c) An electromagnet does not attract a piece of iron. (T/F)
(d) An electric bell has an electromagnet. (T/F)
Ans. 9 (a) To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell. (F)
(b) When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. (T)
(c) An electromagnet does not attract a piece of iron. (F)
(d) An electric bell has an electromagnet. (T)
Que. 10 Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.
Ans. 10 No, an electromagnet can’t be used for separating plastic bags from a garbage heap because they don’t have magnetic properties to get attracted by an electromagnet.
Que. 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.
Ans. 11 No, it is not wise to replace a fuse with a piece of wire because a fuse has a very low melting point, unlike a wire that has a high melting point. In case of a power surge or overload the metallic wire will remain intact increasing the chances of damaging the electric circuits of our house or a probable fire.
Que. 12 Zubeda made an electric circuit using a cell holder shown in Fig. 10.4, 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.
Ans. 12 The possible reasons or defects in the circuit that may be preventing the bulb from glowing can be:
- The connecting wires may be loose.
- Cells in the cell holders may be loose.
- The electric bulb may be fused.
- The switch may be faulty.
- The cells may be used up, etc.
Que. 13 In the circuit shown in Fig. 10.25
(i) Would any of the bulbs glow when the switch is in the ‘OFF’ position?
(ii) What will be the order in which the bulbs A, B and C will glow when the switch is moved to the ‘ON’ position?
Ans. 13 (i) No, the bulbs will not glow when the switch is in the ‘OFF’ position as the electric circuit is incomplete or open.
(ii) When the switch is moved to the ‘ON’ position then all the bulbs will glow simultaneously.
Credits & References
- Class 7th Science NCERT Textbook
- Image by LEEROY Agency from Pixabay
- canva.com
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