Class 7 Science Curiosity Chapter 3 Electricity: Circuits And Their Components NCERT Solutions
Updated for the academic year 2025–26, Class 7 Science Curiosity Chapter 3 – Electricity: Circuits and Their Components NCERT Solutions cover a wide range of topics related to electricity, including circuits, circuit components, circuit diagrams, conductors, insulators, and the functions of various electrical components. In addition, you will learn how to connect a battery to an LED, understand the direction of electric current in a circuit, the uses of a switch, and ways to use electrical symbols to simplify a circuit. These solutions help strengthen your concepts, benefiting you in the long run.
Class 7 Science Curiosity Chapter 3 Electricity: Circuits And Their Components Questions Answers – PDF Download
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1. Choose the incorrect statement.
(i) A switch is the source of electric current in a circuit.
(ii) A switch helps to complete or break the circuit.
(iii) A switch helps us to use electricity as per our requirement.
(iv) When the switch is in ‘OFF’ position, there is an air gap between its terminals.
Answer:
(i) A switch is the source of electric current in a circuit.
A switch is a device that completes or breaks a circuit.
2. Observe Fig. 3.16. With which material connected between the ends A and B, the lamp will not glow?
Answer:
The lamp will not glow when insulating materials like rubber, plastic, and ceramics are connected between ends A and B.
3. In Fig. 3.17, if the filament of one of the lamps is broken, will the other glow? Justify your answer.
Answer:
The current in the circuit flows through a single path, as both bulbs are connected in series. If the filament of one lamp is broken, the circuit becomes open, and the other bulb will not glow.
4. A student forgot to remove the insulator covering from the connecting wires while making a circuit. If the lamp and the cell are working properly, will the lamp glow?
Answer:
No, the lamp will not glow because the insulating cover on the wires prevents current from flowing. The insulation needs to be removed from the connecting wires to establish proper contact between the wires.
5. Draw a circuit diagram for a simple torch using symbols for electric components.
Answer:
6. In Fig. 3.18:
(i) If S2 is in ‘ON’ position, S1 is in ‘OFF’ position, which lamp(s) will glow?
(ii) If S2 is in ‘OFF’ position, S1 is in ‘ON’ position, which lamp(s) will glow?
(iii) If S1 and S2 both are in ‘ON’ position, which lamp(s) will glow?
(iv) If both S1 and S2 are in ‘OFF’ position, which lamp(s) will glow?
Answer:
(i) No lamp will glow because the circuit is broken at S1.
(ii) No lamp will glow because the circuit is broken at S2.
(iii) Both L1 and L2 will glow because the circuit is complete.
(iv) No lamp will glow because the circuit is open at both switches.
7. Vidyut has made the circuit as shown in Fig. 3.19. Even after closing the circuit, the lamp does not glow. What can be the possible reasons? List as many possible reasons as you can for this faulty operation. What will you do to find out why the lamp did not glow?
Answer:
Possible reasons why the lamp doesn’t glow:
(i) The cell is weak or dead.
(ii) The bulb is fused or faulty.
(iii) Loose or faulty connections.
(iv) The safety pin is an insulator or a poor conductor.
(v) Corroded battery terminals.
Things to do to find the problem:
(i) Check the battery.
(ii) Test the bulb.
(iii) Inspect all connections.
(iv) Examine the safety pin and replace it with a good conductor material.
8. In Fig. 3.20, in which case(s) the lamp will not glow when the switch is closed?
Answer:
(a) The switch is closed, current flows, and the lamp glows.
(b) This is the same circuit as (a), but the cell is reversed. The lamp will still glow regardless of the polarity.
(c) LEDs allow current to flow in only one direction. Due to the wrong polarity, the current will not flow and the LED will not glow.
(d) The LED is connected with the correct polarity, so current flows and the LED will glow.
Hence, (a), (b) and (c) are the cases in which the lamps will not glow.
9. Suppose the ‘+’ and ‘–’ symbols cannot be read on a battery. Suggest a method to identify the two terminals of this battery.
Answer:
The two terminals of a battery can be identified using an LED. Connect the battery terminals to the LED in any order. If the LED glows, the battery terminal connected to the positive terminal (longer wire) of the LED is the positive (+) terminal, and the other is the negative (–) terminal.
10. You are given six cells marked A, B, C, D, E, and F. Some of these are working and some are not. Design an activity to identify which of them are working.
(i) List the items that you require.
(ii) Write the procedure that you will follow.
(iii) With the items, carry out the activity to identify the cells that are working.
Answer:
(i) Items Required: A torch bulb, bulb holder, connecting wires and the six cells (A, B, C, D, E, F)
(ii) Procedure:
- Connect the bulb to a cell using the wires.
- Observe if the bulb lights up.
- Repeat the process for each cell (A to F), testing one at a time.
- Record which cells cause the bulb to glow.
(iii) Activity:
If the bulb lights up: The cell is working.
If the bulb does not light up: The cell is not working.
Test all six cells and note which are functional based on the bulb’s response.
11. An LED requires two cells in series to glow. Tanya made the circuit as shown in Fig. 3.21. Will the lamp glow? If not, draw the wires for correct connections.
Answer:
No, the LED will not glow due to incorrect connections.
An LED glows only when its positive terminal (longer wire) is connected to the battery’s positive terminal and its negative terminal (shorter wire) to the negative terminal of the battery.
To correct it:
(i) Connect the positive terminal of the first cell to the negative terminal of the second cell (series connection).
(ii) Connect the free negative and positive terminals to the LED accordingly.