Electricity: Circuits and Their Components Class 7 Question Answer Science Chapter 3

Go through BSE Odisha Class 7 Science Solutions and Class 7 Science Chapter 3 Electricity: Circuits and Their Components Question Answer to understand textbook questions more clearly.

Class 7 Science Curiosity Chapter 3 Question Answer

Science Curiosity Class 7 Chapter 3 Question Answer

Electricity: Circuits and Their Components Class 7 Questions and Answers

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Question 1.
Choose the incorrect statement.

(a) A switch is the source of electric current in a circuit.
(b) A switch helps to complete or break the circuit.
(c) A switch helps us to use electricity as per our requirement.
(d) When the switch is in ‘OFF’ position, there is an air gap between its terminals.
Answer:
(a) A switch does not produce current; it only helps to complete or break the circuit.

Question 2.
Observe the given figure alongside. With which material connected between the ends A and B, the lamp will not glow?
Answer:
The lamp will not glow when an insulator such as rubber, plastic, cork, paper, wood, or glass is connected between the ends A and B.

Question 3.
In the given figure, if the filament of one of the lamps is broken, will the other glow? Justify your answer.

Answer:
No, if the filament of one of the lamps is broken, the other lamp will not glow. This is because both lamps are connected in the same circuit along a single path. When the filament of one lamp is broken, the circuit path gets broken, and the current cannot flow through it.

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:
No, the lamp will not glow. The insulating covering on the wires does not allow an electric current to pass through. As a result, the circuit remains incomplete, and the lamp does not glow.

Question 5.
Draw a circuit diagram for a simple torch using symbols for electric components.
Answer:

A simple torch consists of an electric cell (battery), a switch, and a lamp or an LED connected in a closed circuit. The figure (A) represents the circuit diagram of a torch with a lamp, and figure (B) represents the circuit diagram of a torch with an LED.

Question 6.
In the given figure:

(i) If S₂ is in ‘ ON ‘ position, S₁ is in ‘OFF’ position, which lamps(s) will glow?
(ii) If S₂ is in ‘OFF’ position, S₁ is in ‘ON’ position, which lamps(s) will glow?
(iii) If S₁ and S₂ both are in ‘ON’ position, which lamp(s) will glow?
(iv) If S₁ and S₂ both are in ‘OFF’ position, which lamp(s) will glow?
Ans.
(i) S₂ ON, S₁ OFF: No lamp will glow.
(ii) S₂ OFF, S₁-ON : No lamp will glow.
(iii) S₁ and S₂ – both ON : Both lamps L₁ and L₂ will glow.
(iv) S₁ and S₂ – both OFF: No lamp will glow.
The electric current flows only when the circuit is complete. Both switches S₁ and S₂ must be in ON position to complete the circuit and make the lamps glow.

Question 7.
Vidyut has made the circuit as shown in the figure below. 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:

• The cell may be discharged.
• The circuit is open at some point (for example, a loose or broken connection), so there is no complete path for the current to flow.
• The lamp is fused (its filament is broken), so current cannot pass through it.
• The switch is not properly closed (remains open), so the circuit path is incomplete.
• The ends of the connecting wires are not making metal-to-metal contact because the insulating covering has not been removed, preventing the flow of current.

To find the fault:

• Replace the cell with a new working one to check whether the old cell is weak or discharged.
• Check the switch by turning it ON and ensuring it properly closes the circuit gap.
• Inspect all connections carefully and look for loose or broken joints.
• Tighten the connections so that the bare wire firmly touches the terminals, and there is no insulation in between.
• Test the lamp in another working circuit to confirm whether its filament is intact.

Question 8.
In the figures given below, in which case(s) the lamp will not glow when the switch is closed?
Answer:

In case (c), the LED will not glow when the switch is closed, because it is connected in the reverse direction (positive terminal of LED is connected to the negative terminal of the cell), and current cannot pass through it.

Question 9.
Suppose the ‘+’ and ‘-‘ symbols cannot be read on a battery. Suggest a method to identify the two terminals of this battery.
Answer:
The terminals of a battery can be identified using an LED:

• Connect an LED across the two terminals of the battery.
• If the LED glows, the terminal connected to the longer leg of the LED is positive, and the other terminal is negative.
• If the LED does not glow, interchange the connections. When the LED glows after interchanging, the battery terminal connected to the longer leg of the LED is the positive.

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 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: An electric lamp (or LED), a cell holder, and connecting wires.
(ii) Procedure:

• Prepare a testing setup by connecting the terminals of a bulb (lamp) with two wires.
• Attach the free end of the wires to the two terminals of the cell A and observe whether the lamp glows (If an LED is used instead of a lamp and it does not glow, reverse the connections of the LED and try again).
• If the lamp glows, the cell is working.
• If the lamp does not glow, the cell may be weak or dead.
• Repeat the same process with the remaining cells B, C, D, E, and F, one at a time.

(iii) Observation and conclusion: If the lamp glows upon using a particular cell, it shows that the cell is providing current and is therefore working. If the lamp does not glow, the cell is not supplying current and is therefore not working.

Question 11.
An LED requires two cells in series to glow. Tanya made the circuit as shown in the figure. Will the lamp glow? If not, draw the wires for correct connections.

Answer:
No, the LED will not glow.
The correct connection for the LED to glow is as follows:

Class 7 Curiosity Chapter 3 Question Answer

InText Questions

Question 1.
Why does a torch lamp glow only in one position of the switch? [Page 24]
Answer:
A torch lamp glows only when the circuit is closed. When the switch is ON, the circuit is closed, and electric current flows, so the lamp glows. When the switch is OFF, the circuit is broken, current cannot flow, and the lamp does not glow.

Question 2.
In a torch, we generally use more than one cell. Are those placed in any particular order? [Page 25]
Answer:
Yes. The cells must be placed so that the positive terminal of one cell touches the negative terminal of the next, forming a battery.

Question 3.
Which part of the incandescent lamp glows to produce light? [Page 26]
Answer:
The filament (the thin wire inside the glass bulb) gets hot and glows to produce light.

Question 4.
Sometimes you may come across a device in which the cells are placed side by side. How are the terminals of these cells connected? [Page 31]
Answer:
Inside such a battery compartment, a thick wire or metal strip connects the positive terminal of one cell to the negative terminal of the next.

Question 5.
Why do we use metal wires for making electric circuits? [Page 34]
Answer:
Metal wires (like copper) are used for making electric circuits because metals are good conductors of electricity. They allow electric current to pass through them easily.

Question 6.
Why are electric wires covered with plastic or rubber? [Page 34]
Answer:
Electric wires are covered with plastic or rubber because these are insulators. They prevent electric current from escaping the metal core and entering the human body. This protects users from electric shocks and makes handling wires, plugs, and switches safe.

Question 7.
In the circuit symbol of an LED, what does the direction of the triangle represent, and what do the two outward arrows indicate? [Page 34]
Answer:
In the symbol for an LED, the triangle points to the direction in which the current can flow. The two arrows indicate that light is emitted by an LED.