Students can use Curiosity Class 7 Science Book Solutions Chapter 3 Electricity Circuits and Their Components Class 7 Question and Answer as a quick reference guide.
Class 7 Science Chapter 3 Electricity Circuits and Their Components Question Answer
Science Class 7 Chapter 3 Question Answer Electricity Circuits and Their Components
Electricity Circuits and Their Components Class 7 Question Answer (InText)
Question 1.
Why does the torch lamp glow in one position of its switch? (Page 24)
Answer:
When we slide torch switch forward, the lamp of the torch glows. The switch in this position connects the metal plate inside the torch with the terminal of the lamp to complete the electric circuit. The current flows through the lamp and it glows.
Question 2.
In a torch, we generally use more than one cell. Are those placed in any particular order? (Page 25)
Answer:
All the cells are placed in a torch with their negative terminals towards the spring of the torch.
Question 3.
However, my torch has a different kind of lamp. It cannot be taken out of the torch as it is fixed in it. What is this type of lamp? (Page 26)
Answer:
The LED lamps used in torches these days are the lamps that cannot be taken out of the torch. The earlier incandescent lamps used in torches could be taken out of the torch.
Question 4.
How does a switch turn on or off the torchlight? (Page 32)
Answer:
When we slide torch switch forward, the lamp of the torch glows. The switch in this position connects the metal plate inside the torch with the terminal of the lamp to complete the electric circuit. The current flows through the lamp and it glows.
Question 5.
Can we represent the electric circuits in a simpler manner? (Page 33)
Answer:
To show the electric circuit on a diagram we need not draw, the diagrams of the battery, the lamp and the electric wires and switches etc. We use symbols for these items.
Question 6.
Why do we use metal wires for making electric circuits? Can we not use some other materials for wires? (Page 34)
Answer:
Metals are good conductors of electricity. So, we use metal (generally copper) for making electric wires. Other materials like plastic, rubber, wood etc. . are insulators or bad conductors of electricity. Electric current cannot pass though these materials and these cannot be used for wires.
Question 7.
Why are electric wires covered with plastic or rubber? (Page 34)
Answer:
Electric wires are covered with plastic or rubber. These materials are insulators and save us from electric short circuits or shocks.
NCERT Class 7 Science Chapter 3 Question Answer Electricity Circuits and Their Components (Exercise)
Let Us Enhance Our Learning Exercises (Pages 37-39)
Question 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) is incorrect. (A switch is NOT the source of electric current in a circuit.)
Question 2.
Observe Fig. With which material connected between the ends A and B, the lamp will not glow?
Answer:
If wood, rubber or plastic is connected between the ends A and B, the lamp will not glow. Electric current cannot flow through these materials hence the circuit will not be completed.
Question 3.
In fig., if the filament of one of the lamps is broken, will the other glow? Justify your Answer:.
Answer:
In the electric circuit shown in the diagram, the current passes from positive terminal of the battery to both the lamps one by one and then to the negative terminal of the battery. When filament of one of the lamps is broken the circuit will be broken. None of the lamps will glow.
Question 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:
When the insulator covering from the ends of the connecting wires is not removed, the electric current will not pass through the wires. The lamp will not glow even though the lamp and the cell are working properly.
Question 5.
Draw a circuit diagram for a simple torch using symbols for electric components.
Answer:
A circuit diagram for a simple torch using symbols for electric components is:
Question 6.
In Fig.
(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 Si; 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:
Answer:
(i) S2 ‘ON’, St ‘OFF’: Lamp L2 will glow.
(ii) S2 ‘OFF’, St ‘ON’: Lamp L1 will glow.
(iii) S1 ‘ON’, S2 ‘ON’: Both lamps (L1 and L2) will glow.
(iv) S1 ‘OFF’, S2 ‘OFF’: Neither lamp will glow.
Question 7.
Vidyut has made the circuit as shown in Fig. 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:
The following are the possible reasons of lamp not glowing in the circuit even after closing the circuit:
(a) The filament of the lamp is broken i.e. the lamp is fused.
(b) The connecting wires are connected loosely. The circuit remains broken at the connections.
(c) The insulator coverings are not removed from the ends of connecting wires.
(d) The electric cell is used up and is not serving as a source of electric current.
We will first check the filament of the lamp. If it is broken the lamp will be changed. Next, we will check all connections at the terminals of the cell, lamp and if any connection is found loose, we will connect it properly. Third we will check if the ends of the connecting wires are free from insulating coverings and remove the coverings if not removed. Finally, the battery/cell is to be replaced with a new one.
Question 8.
In Fig. in which case (s) the lamp will not glow when the switch is closed?
Answer:
In case of ‘(c)’ the lamp will not glow. This is an LED lamp and its positive terminal is connected to the negative terminal of the battery.
Question 9.
Suppose the ‘+’ and ‘-‘ symbols cannot be read on a battery. Suggest a method to identify the two terminals of this battery.
Answer:
In an electric cell the metal cap is the Positive terminal and the metallic case is the Negative terminal.
Question 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 actimty 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 for the activity: A lamp holder, connecting wires- two, an incandescent lamp.
(ii) Procedure: Connect the wires to the terminals of the lamp holder with lamp properly fixed in the holder. Ends of the wires should be free from insulating covering. Touch the ends of the two wires to the two terminals of the cell A simultaneously. If the lamp glows, the cell is working. Repeat the activity with all other cells one by one.
(iii) The cells with which the lamp glows on connecting, are working cells and the others are not working cells.
Question 11.
An LED requires two cells in series to glow. Tanya made the circuit as shown in Fig. Will the lamp glow? If not, draw the wires for correct connections.
Answer:
The lamp will not glow as the circuit has not been made correctly. The correct circuit should have positive terminal of the first cell connected to the negative terminal of the second cell. The positive terminal of the second cell should be connected to the positive terminal of the LED and the negative terminal of . the first cell connected to the negative terminal of the LED.
Class 7 Electricity Circuits and Their Components Question Answer (Activities)
Activity 3.6: Let Us Construct (Pages 29-30)
Let us construct. Trying to make the lamp glow.
Answer:
The lamps in case of circuit in the Fig. 1 and Fig. 6 glow and the lamps in rest of the circuits 2, 3, 4 and 5 do not glow. The circuits in 1 and 6 are complete from the positive terminal of the cell to the negative terminal of the cell through the conducting wires and the filament of the lamps.
In 2 and 3 only one terminal of the lamp filament is connected to a terminal of the cell. The circuit is broken. In 4 and 5 both the terminals of the lamp filaments are connected to only one terminal of the cell. The circuit is not complete. It being an incandescent lamp, the circuit is completed without regard to the direction of the current.
Activity 3.10: let Us Draw (Page 34)
Let’s draw the circuit diagrams of Fig. (a) and Fig. (c) using symbols.
Answer:
The circuit diagrams for the given Figures are given here:
Activity 3.11 let Us Identify (Page 35)
Answer:
Table: Identifying Conductors and Insulators
| Object | Material it is made up of | Lamp glows Yes/No | Conclusion (Conductor/ Insulator) |
| Stick | Wood | No | Insulator |
| Scale | Plastic | No | Insulator |
| Bangle | Gold | Yes | Conductor |
| Paper strip | Paper | No | Insulator |
| Candle | Wax | No | Insulator |
| Key | Metal | Yes | Conductor |
| Eraser | Rubber | No | Insulator |
| Handkerchief | Cloth | No | Insulator |
| Copper wire | Metal | Yes | Conductor |
| Coin | Metal | Yes | Conductor |