Electricity Circuits and Their Components Class 7 Questions and Answers Science Chapter 3

Reviewing the Curiosity Class 7 Science Book Solutions Chapter 3 Electricity Circuits and Their Components Class 7 Question and Answer before exams can boost your confidence.

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:
The torch lamp glows in one position of its switch because in that position, the electric circuit is complete. When the circuit is complete, electric current flows from the battery through the bulb, which makes the bulb glow. In the other position of the switch, the circuit is broken, so the current does not flow and the bulb 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, in a torch, cells are placed one after another in a line, with the positive end of one cell touching the negative end of the next. This is called series connection, and it helps increase the total voltage to make the bulb glow brighter.

Question 3.
How does a switch turn ON or OFF the torchlight? (Page 32)
Answer:
A switch controls the torchlight by opening or closing the circuit. When the switch is ON (closed), it allows electricity to flow from the battery to the bulb, turning the light ON. When the switch is OFF (open), it breaks the circuit, stopping the flow of electricity, which turns the light OFF.

Question 4.
Can we represent the circuits in a simple manner? (Page 33)
Answer:
Yes, we can represent circuits in a simple way using circuit diagrams.

Question 5.
Why does we use metal wires for making electric circuits? Can we not use some other materials for wires? (Page 34)
Answer:
We use metal wires like copper in electric circuits because metals are good conductors of electricity, meaning they allow electricity to flow easily through them. Other materials, like rubber or wood, are poor conductors and would not let electricity flow effectively. While there are some other materials that can conduct electricity (like aluminum), metals are typically chosen because they are efficient, durable and easy to work with.

Question 6.
Why are electric wires covered with plastic rubber? (Page 34)
Answer:
Electric wires are covered with plastic or rubber to insulate them. This means the plastic or rubber prevents electricity to flow from outside the wire. It also protects the wire from damage, moisture and heat, ensuring safety and preventing electrical shocks or short circuits.

NCERT Class 7 Science Chapter 3 Question Answer Electricity Circuits and Their Components (Exercise)

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; the battery or cell is the source. A switch only helps to start or stop the flow of current.

Question 2.
Observe the figure given below. With which material connected between the ends A and B will the lamp not glow?

Answer:
The lamp will not glow if a non-conducting material (insulator) like plastic, rubber or wood is connected between A and B. These materials do not allow electric current to pass through them.

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

Answer:
No, the other lamp will not glow. Both lamps are connected in series. If the filament of one lamp breaks, the circuit becomes open and current cannot flow. So, both lamps will stop glowing.

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 plastic insulator does not allow electric current to pass. So, even if the cell and lamp are fine, the current won’t flow and the lamp won’t glow.

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

Question 6.
In the figure given below
(i) If S₂ is in ON position, S₁ in OFF position, which lamp(s) will glow?
(ii) If S₂ is in OFF position, S₁ 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 lamps will glow.
(ii) Neither lamps will glow.
(iii) Both lamps L₁ and L₂ will glow.
(iv) Neither lamps will glow.

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

The cell might be dead (no power).
The bulb might be fused or damaged.
The wires might be loose or broken.
The switch might not be working.
There might still be plastic covering (insulator) on the wire ends.

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

Answer:
In case (b) The wires are not connected to the lamp in the proper order. So, the lamp will not glow.
In case (d) The LED is connected in the wrong direction. LEDs only work in one direction, so it will not glow.
So, the lamp will not glow in cases (b) and (d).

Question 9.
Suppose the ‘+’ and symbols cannot be read on a battery. Suggest a method to identify the two terminals of this battery.
Answer:
Use a simple circuit with a small bulb.
(i) Items required A small torch bulb, two connecting wires, the battery (with hidden terminals).

(ii) Procedure
• Connect the bulb and battery using wires.
• Try one connection first. If the bulb glows, mark the terminals as V and ‘-‘
• If it doesn’t glow, reverse the connection. If it glows now, note the new V and terminals.

(iii) Activity result
• The glowing bulb helps identify the battery terminals.
• The terminal connected to the bulb’s bottom (metal tip) is the positive terminal (+).
• The other terminal 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 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 small bulb, two wires, six cells (A-F)
(ii) Procedure

1. Connect the bulb with one cell using two wires.
2. If the bulb glows, the cell is working.
3. If the bulb does not glow, the cell is not working.
4. Repeat this for all six cells one by one.

(iii) Activity result
The cells that make the bulb glow are working and those that don’t are not working.

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

Answer:
No, the lamp will not glow. The two cells are not connected correctly in series. Both positive terminals are connected together, which is wrong.

Class 7 Electricity Circuits and Their Components Question Answer (Activities)

Activity 1 (Page 24)

Aim To observe how a torchlight glows using an electric circuit.
Materials Required A torchlight (with battery and lamp inside), a switch (part of torch) and electric cells.

Procedure

Take a torchlight similar to the one shown in the figure
Observe it carefully. Notice the lamp and the switch.
Slide the switch to the ON position and observe the lamp.
Now slide the switch back to its original (OFF) position.
Open the torchlight and check what is inside – you may find two or more electric cells.

Observation:
The torch lamp glows in one position of the switch and does not glow in the other.

Conclusion:
The torch lamp glows when the switch completes the circuit (closed circuit) and allows electric current to flow from the cells to the lamp. When the switch is OFF (open circuit), the current does not flow, so the lamp does not glow.

Viva Questions
1. What role does the switch play in making the torchlight useful?
2. Why do you think the lamp doesn’t glow when you slide the switch back?
3. If there were no electric cells inside the torch, would sliding the switch make any difference?
4. Why is it important to observe the number of cells inside a torchlight?

Activity 2 (Page 25)

Aim To observe the physical features and identify the positive and negative terminals of an electric cell.
Material Required One electric cell.

Procedure

Take an electric cell and observe it carefully as shown in figure below.
Rotate the cell and look for any markings on its body.
Identify the positive (+) and negative (-) signs marked on the cell.
Observe the two ends of the cell-one has a metal cap and the other has a flat metal disc.

Observation:
The electric cell has a positive terminal marked with a plus (+) sign and a metal cap.
The other end has a negative terminal marked with a minus (-) sign and a flat metal disc.

Conclusion:
The electric cell has two terminals, a positive terminal (metal cap) and a negative terminal (metal disc). These terminals are essential for the flow of electric current. The electric cell is a portable source of electrical energy.

Viva Questions
1. How many terminals does an electric cell have?
2. How can you identify the positive terminal of a cell?
3. What does the flat metal disc of a cell represent?
4. Why is it important to know the terminals of an electric cell?

Activity 3 (Page 25)

Aim To observe how cells must be placed correctly in a torch for the lamp to glow and understand the concept of a
battery.
Materials Required A torch that uses two electric cells.

Procedure

Open the cell compartment of the torch and remove the two cells.
Observe the original placement and direction of the cells.
Now, place the cells back in a different order or reverse the direction of one cell.
Slide the switch of the torch and observe whether the lamp glows.
Try placing the cells as they were originally placed and slide the switch again.

Observation:
The lamp does not glow when the cells are placed incorrectly or when one cell is reversed. The lamp glows only when the positive terminal of one cell is connected to the negative terminal of the next cell as shown in figure.

Conclusion:
The torch works only when the cells are connected in a proper order the positive terminal of one cell to the negative terminal of the next. This arrangement forms a battery. Connecting multiple cells in this way increases the energy supplied to the circuit.

Viva Questions
1. What happens when cells in a torch are placed in the wrong order?
2. How should cells be connected in a torch for it to work properly?
3. What is a battery?
4. Why do we use more than one cell in some devices?
5. What is the function of a torch?

Activity 4 (Page 26)

Aim To observe the structure and working of the filament inside an incandescent lamp used in a torch.
Materials Required A torchlight with an incandescent lamp and teacher’s assistance for handling the lamp safely.

Procedure

Confirm with your teacher that the torchlight contains an incandescent lamp.
Carefully examine the lamp while it is off.
Observe the inside of the glass bulb. Note the thin wire (filament) fixed in the centre.
Now, switch ON the torch and observe which part of the lamp glows.
With the help of your teacher, safely remove the lamp from the torch.
Check the base of the lamp and observe how the filament is connected to other parts.

Observation:
A thin wire is present in the middle of the glass bulb. This is the filament. When the torch is turned ON, only the filament glows, producing light. The filament is held by two thicker support wires as shown in Fig. (a) and one thick wire connects to the metal case at the base and the other connects to the metal tip at the centre of the base as shown in Fig. (b). These two wires form the two terminals of the lamp and are fixed such that they do not touch each other.

Conclusion:
The filament is the part of the incandescent lamp that glows to produce light. It is connected to two terminals through thick wires. When electric current passes through the filament, it becomes hot and emits light. The terminals ensure that the current flows correctly through the filament without short circuiting.

Viva Questions
1. What is the name of the thin wire that glows in a lamp?
2. What happens to the filament when the torch is switched ON?
3. How is the filament connected inside the bulb?
4. What are the two terminals of the lamp?
5. Why don’t the two terminals of the lamp touch each other?

Activity 5 (Page 27)

Aim To observe an LED closely to identify the presence or absence of a filament and distinguish its terminals based on wire length.

Materials Required LED (any colour), magnifying glass (optional), electric cell or battery, connecting wires, switch (optional).

Procedure

Take an LED of any colour as shown in figure below and hold it carefully.
Observe the inner structure of the LED using naked eye or a magnifying glass.
Note whether there is any filament inside the LED like in an incandescent lamp.
Observe the two metallic legs (wires) coming out of the LED.
Compare the length of the two wires-identify the longer and shorter wires.
Connect the longer wire (positive terminal) of the LED to the positive terminal of the electric cell and the shorter wire (negative terminal) to the negative terminal of the electric cell.
Observe if the LED glows.
Reverse the connection and observe whether it still glows.

Observations:
The LED does not contain any filament as shown in figure.
The LED has two wires of different lengths-the longer is positive, the shorter is negative.
The LED glows only when connected in the correct direction.

Conclusion:
LEDs work differently from incandescent lamps. They do not have a filament and work on the principle of allowing current to pass only in one direction. The longer wire is the positive terminal and the shorter wire is the negative terminal. LEDs are energy-efficient and safe for simple circuit experiments.

Viva Questions
1. If an LED doesn’t glow even when connected to a battery, what could be a possible reason besides a damaged LED?
2. Why do you think we don’t see a glowing wire inside an LED, unlike in a torch bulb?
3. Without touching the LED terminals to a battery, how can you tell which wire is positive?
4. If a torch uses multiple LEDs of different shapes, can they be connected randomly? Why or why not?
5. Why are LEDs more energy-efficient than traditional filament bulbs?

Activity 6 (Page 27 and 28)

Aim To study how an incandescent lamp can be made to glow using an electric cell and observe how different connections affect the result.

Materials Required Electric cell, incandescent lamp (torch bulb), cell holder (optional), lamp holder (optional), four pieces of electric wire, electrical tape, wire stripper or scissors (to remove insulation).

Procedure

Take four pieces of electric wire and remove about 1 cm of insulation from both ends of each wire.
Connect two wires to the two terminals of the cell holder as shown in (Fig. a). If a cell holder is not available, fix the wires directly to the cell using electrical tape (Fig. c).
Insert the electric cell into the holder ensuring the negative terminal is towards the spring side (Fig. b).
Connect two wires to the lamp holder’s screws as in (Fig. d) and fix the incandescent lamp into the holder (Fig. e). If the holder is not available, use electrical tape to connect wires directly to the lamp terminals (Fig. f).
Try different ways of connecting the cell and lamp using the wires.
For each connection method, predict whether the lamp will glow or not and write it down in the table.
Then perform the actual connection and record your observation.
For each case where the lamp glows, colour the lamp yellow in the table to indicate glowing.

Prediction and Observation Table

Connection type	Your prediction (glow/not glow)	Observation (glow/not glow)	Colour if glowed
1. One wire from each terminal to lamp
2. Both wires from same cell terminal
3. Lamp Connected without full circuit
4. Cell terminals reversed
5. Proper complete circuit			Yellow

Conclusion:
The lamp glows only when a complete circuit is formed and the current flows from the positive to the negative terminal of the cell, passing through the lamp. Improper or incomplete connections prevent the lamp from glowing.

Viva Questions
1. Why does the lamp glow only in some arrangements even though it is connected to a cell?
2. What would happen, if both wires are connected to the same terminal of the cell?
3. In your own words, what is the role of the lamp holder in this setup?
4. What does this activity tell us about electric circuits?

Activity 7 (Page 30 and 31)

Aim To observe that an LED glows only when connected in the correct direction (polarity) in a circuit.

Materials Required 2 electric cells, 1 LED (any colour), 1 cell holder (for two cells), 2 electric wires, wire stripper or scissors (to remove insulation).

Procedure

Remove about 1 cm of insulation from both ends of the two wires.
Connect one wire to each terminal of the two cell holder (Fig. a).
Insert two cells in the holder, ensuring that the negative terminal of each cell is toward the spring side (Fig. b). This completes the battery.
Identify the longer leg of the LED (positive terminal) and the shorter leg (negative terminal).
Connect the wire from the positive terminal of the battery to the longer leg of the LED. The wire from the negative terminal of the battery to the shorter leg of the LED.
Observe whether the LED glows ( Fig. c).
Now reverse the connections Connect the battery’s positive wire to the shorter leg, then connect the battery’s negative wire to the longer leg.
Observe again, if the LED glows (Fig. d).

Observation

Connection direction	Observation
Correct polarity (positive to longer leg)	LED glows
Reversed polarity (positive to shorter leg)	LED does not glow

Conclusion:
The LED allows current to pass in only one direction. It glows only when the positive terminal of the battery is connected to the longer leg (positive) of the LED and the negative terminal to the shorter leg (negative) of the LED. LEDs are unidirectional devices.

Viva Questions
1. If an LED is connected but does not glow, what might be a likely reason besides a faulty LED?
2. How can you identify the positive terminal of an LED without using any instruments?
3. Why do we use two cells in this experiment and not one?

Activity 8 (Page 32)

Aim To construct a simple electrical switch using household materials and test its working in an electric circuit.

Materials Required 2 drawing pins,l safety pin (or paper clip), 2 electric wires, small piece of cardboard, battery (cell), bulb with holder, electrical tape (if needed).

Procedure

Take a small cardboard piece as the base.
Fix one drawing pin through the round part of the safety^ pin and press it into the cardboard so that the safety pin can move easily (Fig. a).
Fix the second drawing pin a little away on the cardboard so that the free end of the safety pin can touch it (Fig. b).
Connect one wire to each drawing pin.
Now connect the wires from the switch into a simple circuit with a battery and a bulb.
When the safety pin touches the second drawing pin, the bulb glows.
When the safety pin is lifted, the bulb turns OFF.

Observation

Switch position	Contact between pins
Closed	Safety pin touches second pin
Open	Safety pin does not touch

Conclusion:
This setup acts as a basic switch. When the safety pin touches the second drawing pin, the circuit is complete and the bulb glows. When the contact is broken, the circuit is open and the bulb turns OFF. Thus, a safety pin can be used to make a functional homemade switch.

Viva Questions
1. Why does the bulb glow only when the safety pin touches the second pin?
2. What kind of switch is this: automatic or manual?
3. What material property makes the safety pin work in this setup?
4. What would happen if we used a plastic pin instead of a metal safety pin?
5. Can this switch be used to control any electric device?

Activity 9 (Page 32)

Aim To understand how a switch opens and closes an electric circuit and controls the flow of electric current.

Materials Required 1 electric cell, 1 torch bulb with holder, 2 drawing pins, 1 safety pin (or paper clip), 1 small cardboard piece, 2 electric wires, electrical tape (if needed).

Procedure

Fix the safety pin on the cardboard using one drawing pin so that it can move freely.
Fix the second drawing pin a little away on the cardboard, so that the free end of the safety pin can touch it.
Connect one wire to each drawing pin to complete the switch.
Now, connect the electric cell, lamp and the switch using wires as shown in Fig. (a).
First keep the safety pin away from the second drawing pin. Observe the lamp – it does not glow.
Now rotate the safety pin to touch the second drawing pin (Fig.b). Observe again – the lamp glows.

Safety pin position	Circuit status	Lamp glows
Not touching second pin	Open( OFF )	No
Touching second pin	Closed (ON)	Yes

Conclusion:
When the safety pin touches both drawing pins, it completes the circuit and the lamp glows. This is the ON position. When the safety pin is away, the circuit is broken and the lamp does not glow. This is the OFF position. So, a switch controls the flow of current by opening or closing the circuit.

Viva Questions
1. What is the purpose of a switch in an electric circuit?
2. Can a switch be placed anywhere in a circuit?
3. What does the lamp glowing indicate about the circuit?
4. What is meant by an open circuit?

Activity 10 (Page 34)

Aim To draw circuit diagram using correct symbols for electrical components.
Materials Required Pencil, ruler, notebook, your textbook (for circuit pictures and symbols).

Procedure
1. Look at the circuit table as shown in Fig (a) to find the correct symbols for parts like battery, bulb LED and switch from table.

2. Now draw the circuit diagram of an electrical circuit given in Fig. (a) and Fig. (b).

3. Make sure you show the positive and negative ends correctly.
4. Finally, compare your circuit diagram with the ones shown in Fig. (c) and Fig. (d) to check if they are same.

Conclusion:
Yes, the circuit diagrams drawn using standard symbols matches with Fig. (a) and fig (b).

Viva Questions
1. Why do we use symbols instead of pictures in circuit diagrams?
2. What is the difference between a lamp and an LED in a circuit diagram?
3. If a bulb is not glowing in a circuit, what could be the possible reasons in terms of the diagram?
4. In the circuit with the LED, why does it glow only when connected in one particular direction?
5. How is a battery represented in a circuit diagram?

Aactivity 11 (Page 35)

Aim To identify materials that allow electric current to pass through them (conductors) and those that do not (insulators) using a simple electric tester.
Materials Required 1 electric cell, 1 torch bulb with holder and 2 electric wires

Objects to Test:
Metal spoon, coin, cork, rubber, glass piece, key, pin, plastic scale, wooden block, aluminium foil, candle, sewing needle, cardboard, paper, pencil lead, etc.

Procedure

Connect one wire from the positive terminal of the electric cell to one side of the lamp holder.
Connect another wire from the other side of the lamp holder to the negative terminal of the cell (as shown in Fig. a).
Leave two free ends of the wires extending from the tester.
Now, momentarily touch the two free ends together. If the lamp glows, your tester is working.
One by one, place each object (like a coin, spoon, rubber) between the free ends of the tester wires (see Fig. b).
Ensure both ends of the object touch the wires and the wires do not touch each other.
Observe whether the lamp glows.
Record the results in table.

Object tested	Does the lamp glow?	Conclusion (Conductor/ Insulator)
Metal spoon	Yes	conductor
Coin	Yes	Conductor
Rubber	No	Insulator
Glass piece	No	Insulator
Aluminium foil	Yes	Conductor
Plastic scale	No	Insulator
Wooden block	No	Insulator
Candle	No	Insulator
Sewing needle	Yes	conductor

Conclusion:
Objects that allow the bulb to glow are conductors, which allow electric current to pass through them. Objects that do not make the bulb glow are insulators, which resist the flow of electric current.

Viva Questions
1. Why do we touch the two free ends of the tester wire before testing the materials?
2. What does it mean if the lamp does not glow even after connecting a material?
3. Can you name a material that is not a metal but still conducts electricity?
4. Why must we ensure that the two wires of the tester do not touch each other while testing?
5. Is water a conductor or an insulator?