Find NCERT Solutions to Class 7 Science Curiosity Chapter 3 right here! We have explained all the essential concepts related to electrical circuits in this material. Make sure you look at the diagrams property and understand them while studying. Class 7 Science Curiosity Chapter 3 Electricity: Circuits and their Components can be a very interesting topic if you understand the basics and you will see conceptual questions from this topic in your exams. So, understand it well!
Good luck!
Let Us Enhance Our Learning (Class 7 Science Curiosity Chapter 3):
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: Incorrect statement: (i) A switch is the source of electric current in a circuit.
Explanation: A battery is the source of electric current in a circuit. A switch is used to complete or break 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 if insulating materials like wood, plastic, glass, paper, wax, rubber is connected between the 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:
If the filament of one of the lamps is broken, the other will not glow because the broken filament will break the circuit and current will not flow through it.
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. This is because the insulator covering will prevent proper contact between the wires and the two terminals of the battery and also the lamp.
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) Neither lamp will glow because the circuit is broken due to S1 being open.
(ii) Neither lamp will glow because the circuit is broken due to S2 being open.
(iii) Both lamps will glow because it is a closed circuit.
(iv) Neither lamp will glow because the circuit is broken due to S1 and S2 being open.
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:
The possible reasons for the lamp not glowing are as follows:
(i) The bulb is fused because the filament is broken.
(ii) The battery is faulty or exhausted.
(iii) The wires are faulty or loosely connected.
(iv) The safety pin is made up of an insulating material.
(v) The tape used to connect the wires is insulating.
To find out why the lamp did not glow we will one by one test each component:
(i) Check if the cell is positioned correctly such that its negative terminal is towards the spring side of the holder.
(ii) Test the battery to see if it is exhausted or not.
(iii) Test the lamp to check whether the filament is intact.
(iv) Inspect the wires for signs of damage.
(v) Inspect the connections to see if they are loose.
(vi) Inspect the switch to see if it is made of conducting material.
(vii) Then inspect the functioning of the switch by connecting the battery directly to the bulb using conducting wires.
8. In Fig. 3.20, in which case(s) the lamp will not glow when the switch is closed?
Answer:
(a) When the switch is closed, the bulb glows because current flows through the closed circuit.
(b) When the switch is closed, the bulb glows even though the terminals are reversed because the circuit is closed.
(c) When the switch is closed current flows from the positive terminal of the battery to the negative terminal of the battery in a counterclockwise direction. However, the symbol for the LED indicates that current can only flow from left to right in a clockwise direction. Therefore, due to wrong direction current will not flow through the closed circuit.
(d) When the switch is closed current flows from the positive terminal of the battery to the negative terminal of the battery in a clockwise direction. The symbol for the LED indicates that current can only flow from left to right in a clockwise direction. Therefore, due to correct direction current will flow through the closed circuit.
9. Suppose the ‘+’ and ‘–’ symbols cannot be read on a battery. Suggest a method to identify the two terminals of this battery.
Answer:
To find the positive and negative terminals of a battery, you can use an LED:
- Connect the LED to the battery terminals in any order.
- If the LED lights up, the wire connected to the longer legof the LED is attached to the positive (+) terminal of the battery, and the other is the negative (–) terminal.
- If the LED does not glow, reverse the connections and try again.
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)
Materials Required:
(a) A bulb
(b) A bulb holder
(c) Connecting wires
(d) A cell holder
(ii)
Procedure:
Step 1: Insert the cell in the holder such that its negative terminal is towards the spring side of the holder. In case a cell holder is not available, fix the two wires to the cell using electrical tape.
Step 2: Attach two wires to the screws of the lamp holder. Fix the lamp in the holder by turning it around in the holder. In case a lamp holder is not available, use electrical tape to attach two wires to the two ends of the lamp.
Step 3: Now, connect the lamp and each cell, and observe if the lamp glows or not.
Step 4: Note which of the cells A, B, C, D, E, and F cause the battery to glow.
Conclusions: If the cells cause the bulb to glow we conclude that they work.
(iii) Have fun carrying out the activity on your own!
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:
The LED will not glow in Fig. 3.21 because the positive terminal of the LED (longer wire) is connected to the positive terminal of the battery and the negative terminal of the LED (shorter wire) is connected to the negative terminal of the other battery.
The setup with the correct connections is shown below:
As you can see the positive terminal of one cell is connected to the negative terminal of the second cell. Also, the positive terminal of the LED (longer wire) is connected to the positive terminal of the battery and the negative terminal of the LED (shorter wire) is connected to the negative terminal of the other battery.
Hope you enjoyed our solutions material on Class 7 Science Curiosity Chapter 3! Click on the links below to access the solutions to the remaining chapters!
Related Links:
Chapter 1 The Ever-Evolving World of Science
Chapter 2 Exploring Substances: Acidic, Basic, and Neutral
Chapter 3 Electricity: Circuits and their Components
Chapter 4 The World of Metals and Non-metals
Chapter 5 Changes Around Us: Physical and Chemical
Chapter 6 Adolescence: A Stage of Growth and Change
Chapter 7 Heat Transfer in Nature
Chapter 8 Measurement of Time and Motion
Chapter 9 Life Processes in Animals
Chapter 10 Life Processes in Plants
Chapter 11 Light: Shadows and Reflections
Chapter 12 Earth, Moon, and the Sun
