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Class 7 Science Chapter 3 Electricity Circuits and Their Components Extra Questions
Class 7 Science Chapter 3 Extra Questions on Electricity Circuits and Their Components
Electricity Circuits and Their Components Class 7 Very Short Question Answer
Question 1.
Name the device which is used as a source of electricity while working in school labs.
Answer:
Electric cell or battery
Question 2.
What is inside an electric cell that is used to produce electricity?
Answer:
Chemicals.
Question 3.
Why wires made of copper are used in electric circuits?
Answer:
Copper is a good conductor of electricity and a less costly metal.
Question 4.
Why we do not connect the positive terminal of a cell to its negative terminal directly?
Answer:
The chemicals inside the cell may be used up fully and the cell may become non-working.
Question 5.
A lamp and an electric cell both have two terminals each. Which terminals are marked *+* and sign?
Answer:
In electric cell the metallic top is marked ‘+’ and metallic case is marked Terminals in incandescent lamp are not marked. Long wire of an LED lamp is the ‘+’ terminal and short wire is the terminal.
Question 6.
What is an electric circuit?
Answer:
The path provided to electricity to flow through an electric wire or a device.
Question 7.
All the connections in a circuit are correct but the lamp does not glow, what could be the reason?
Answer:
Filament of the lamp could be broken i.e. the lamp may be fused.
Question 8.
Why we use switches in electric circuits?
Answer:
Switches in electric circuits are used to make or break the circuit when required.
Electricity Circuits and Their Components Class 7 Short Question Answer
Question 1.
In a circuit we do not have a switch. In place of the switch, we use the following objects one by one. In which cases a, b, c, or d the lamp will glow and in which case it will not glow and why?
(a) A metal key
(b) A plastic scale
(c) A cotton thread
(d) A safety pin
Answer:
In case of a metal key or a safety pin, the lamp will glow. The current passes easily through metals and hence the circuit will be complete.
Question 2.
What is the direction of current flow shown in a circuit? Why this direction is shown?
Answer:
It is a convention to show the flow of current from positive to negative terminal in an electric circuit.
Question 3.
What part of a torch lamp glows when we switch on the torch? What will happen if this part breaks?
Answer:
Filament of the electric lamp glows when we switch on the torch. When filament breaks, the lamp does not glow to produce light.
Question 4.
What is an electric cell? What happens when the chemicals stored in the cell are used up?
Answer:
An electric cell is a portable source of electric current. It works on the chemicals stored inside the cell. When the chemicals stored in the cell are used up, the cell stops working and cannot be used in a circuit.
Question 5.
What is an electric circuit? What items would you require to make a complete electric circuit?
Answer:
The path provided to electricity to flow through an electric wire or a device.
An electric cell or a battery, conducting wires, an electric switch and an electric lamp are required to make a complete electric circuit.
Question 6.
What are the uses of an electric cell?
Answer:
We use electric cells in TV remotes, torches, some toys, cameras and similar devices.
Electricity Circuits and Their Components Class 7 Long Question Answer
Question 1.
Draw an electric circuit using a cell, a lamp, three conducting wires and a switch. Show the position of the switch when the lamp glows. ‘ Explain why we need to complete the circuit.
Answer:
The required electric circuit is:
When the lamp glows the position of the switch is ON (it touches the wire on both ends.
We need to complete the circuit to make the current flow through the circuit. When the current flows through the filament of the lamp, it glows.
Question 2.
What are conductors and insulators? Give three examples each of the conductors and insulators.
Answer:
Materials through which electric current passes easily are called good conductors of electricity or conductors of electricity.
Examples of good conductors are items made of metals like wires, keys, safety pin, metal spring etc.
Materials through which electric current cannot pass are known as insu¬lators or bad conductors of electricity.
Examples of insulators or bad conductors are items made of plastics, rubber and wood like plastic scale, rubber eraser, wooden stick etc.
Question 3.
(a) In a complete electric circuit the lamp does not glow. What are the possible reasons?
(b) How is a lamp fused?
(c) If we connect a cell with used up chemicals in a circuit, will the lamp glow? If not why?
Answer:
(a) The possible reasons for an electric lamp not glowing in a complete electric circuit are:
- Filament of the lamp is broken
- Wires loosely connected
- Cell fully used up and not working
- When LED lamp is used, the terminals are not connected in correct order (positive terminal of the cell should be connected to the long wire of the LED lamp).
(b) When the filament of an electric lamp is broken the lamp is said to be fused.
(c) If we connect a cell with used up chemicals in a circuit, the lamp will NOT glow. The cell with used up chemicals cannot provide the desired electric current.
Question 4.
Name the items required for making a complete circuit. What precautions are required to make a correct circuit?
Answer:
An electric cell or a battery, conducting wires, an electric switch and an electric lamp are required to make a complete electric circuit.
Precautions required to make a correct circuit are:
- The lamp used in the circuit should not have a broken filament.
- The insulating covering should be removed from the ends of connecting wires before connecting.
- Wires must be connected properly and should not be left loose.
- Cell used in the circuit ‘must be in working condition and not used up.
- When LED lamp is used, the terminals must be connected in correct order (positive terminal of the cell should be connected to the long wire of the LED lamp).
Electricity Circuits and Their Components Class 7 Case Based Questions
I. A torch lamp has an outer case made of glass fixed on a metal base. Within the outer case a curved thin wire is visible. This is supported by and hanging on two thick wires. This curved thin wire is the filament of the lamp. When the torch is switched on this filament glows in the lamp.
The thick wires are standing inside the case on the metal base. One of the two standing thick wires is connected to a metal tip at the centre of the base. The other thick wire is connected to the metal case.
Answer the following questions:
Question 1.
What component of the torch glows when we switch on the torch?
Answer:
The filament of the torch lamp glows on switching on the torch.
Question 2.
Which are the two terminals of the torch lamp?
Answer:
The thick wires are standing inside the case on the metal base. One of the two standing thick wires is connected to a metal tip at the centre of the base. The other thick wire is connected to the metal case. The metal tip at the centre of the base of lamp is one terminal and the metal case is the second terminal.
Question 3.
Do LED lamps have filaments?
Answer:
LED lamps do not have filaments.
Question 4.
What is the difference between connecting an incandescent lamp and connecting an LED lamp in an electric circuit?
Answer:
We need not to differentiate between positive terminal and the negative terminal in case of incandescent lamp in a circuit. In case of LED lamp, the longer wire of the lamp has to be connected to the positive terminal of the source of electric current (cell or a battery).
II. It must be noted that the electric current flows through an electric circuit in case the circuit is completed properly with the conducting wires. Circuit has to be complete with a path from the positive terminal of the cell to its negative terminal. To make a complete circuit, the positive terminal of the cell has to be connected to one of the terminals of the lamp. The two terminals of the lamp must be connected internally through the filament. The second terminal of the lamp must be connected to the negative terminal of the cell.
Answer the following questions:
Question 1.
When an electric circuit considered to be complete?
Answer:
To make a complete circuit, the positive terminal of the cell has to be connected to one of the terminals of the lamp. The two terminals of the lamp must be connected internally through the filament. The second terminal of the lamp must be connected to the negative terminal of the cell.
Question 2.
Define an effective circuit.
Answer:
The path provided to electricity to flow through an electric wire or a device is called an electric circuit. An electric cell or a battery, conducting wires, an electric switch and an electric lamp are required to make a complete electric circuit.
Question 3.
What is the direction of the flow of electric current in an electric circuit?
Answer:
As a convention, the electric current is represented by arrows as flowing from the positive terminal of the cell or the battery to its negative terminal through the conducting wires, electric device (filament of the lamp) and a switch in the ON position.
Question 4.
When a switch in an electric circuit is in the OFF position or the filament of the electric lamp is broken, does the current flow through the circuit?
Answer:
The current does not flow as the switch is in OFF position or a broken filament, breaks the circuit.
Electricity Circuits and Their Components Extra Questions for Practice
Very Short Answer Type Questions
Question 1.
What is a portable source of electric energy?
Question 2.
Which devices are used to produce electricity from wind energy?
Question 3.
Name three uses of electricity in our houses.
Question 4.
Why do we remove about 1 cm of plastic covering from the ends of wires before connecting them?
Question 5.
What happens if the filament of an incandescent lamp breaks in a complete circuit?
Question 6.
What are the two terminals of an LED lamp?
Question 7.
Are the two terminals of an incandescent lamp different for connection in a circuit?
Question 8.
Write the direction of flow of electric current in a circuit.
Short Answer Type Questions
Question 1.
Do the LED lamps have filaments? Are the terminals of the LED lamp different from those of an incandescent lamp?
Question 2.
Draw a simple electric circuit using a cell, three wires and a lamp.
Question 3.
What is a circuit diagram?
Question 4.
What do these symbols in an electric circuit represent?
Question 5.
What is the difference between the lamps in Figures (a) and (b)?
Question 6.
What is the use of symbols in drawing a circuit diagram?
Question 7.
Name three materials that are electric insulators and three items that are good conductors of electricity.
Question 8.
What is the correct position of a switch in an electric circuit?
Long Answer Type Questions
Question 1.
Define an electric circuit. How do we differentiate between an incandescent lamp and an LED lamp in electric circuits? What precautions are taken while making an electric circuit?
Question 2.
What is the direction of electric current in a circuit? What happens to the flow of electric current if:
(a) The incandescent lamp in the circuit has a broken filament.
(b) The plastic insulation is not removed from the ends of the connecting wires before making connections.
(c) The switch is connected on the side of the negative terminal of the cell instead of positive terminal of the cell.
(d) The metal tip of the incande¬scent lamp is connected to the negative terminal of the cell and the metal cap of the lamp is connected to the positive terminal of the cell.
Question 3.
Draw circuit diagrams using symbols with an LED lamp in the circuit showing the two positions of the switch when
(i) the lamp does not glow and
(ii) when the lamp glows.
Question 4.
Why a danger sign is displayed on electric poles with high tension wires? What do we use as a source of electricity while performing activities and experiments related to electric current in our school laboratory?
Case/ Source Based Question
I. We need conducting wires to connect a bulb to the electric cell for various activities. The conducting wires are made of copper or aluminium wires covered with plastic or rubber material.
Question 1.
Why are electric conducting wires made of copper or aluminium, covered with plastic or rubber material?
Question 2.
Before connecting the bulb and the cell, we need to remove a little of the plastic covering from the ends of these wires. We connect the metal part of the wire with the terminals. Explain why?
Question 3.
If we connect the short wire of the LED lamp to the positive terminal of the cell with a wire, will the lamp glow? If not, why?
Question 4.
If metal inside the plastic coating in a wire is broken, how this wire connected in a circuit will affect the flow of current in the circuit?
Multiple Choice Questions (MCQs)
Choose the correct option in the following questions:
Question 1.
Insulators or bad conductors of electricity are the materials that:
(a) Allow electric current to pass through them easily
(b) Enhance the electric current passing through them
(c) Do not allow electric current to pass through them
(d) Help to make or break an electric circuit when required
Question 2.
Electric current in an electric circuit flow from positive terminal of the _________ to the negative terminal of the
(a) cell, lamp
(b) lamp, lamp
(c) lamp, cell
(d) cell, cell
Question 3.
The spring at the back end of the torch –
(a) holds the cells of the battery tightly to keep them in position
(b) serves as a conductor in the circuit
(c) is connected to the lamp through a wire or the metal cover of the torch
(d) all of these
Question 4.
Conducting wires in an electric circuit should be
(a) Loosely connected to the terminals
(b) Joined together on one end and joined to one terminal of the cell on the other end
(c) Insulation free from both ends before connecting in a circuit
(d) Made of plastic threads only
Question 5.
When the chemicals in a cell are fully used up
(a) The cell stops working
(b) The energy of the cell increases
(c) Flow of current improves in the circuit
(d) The cell terminals interchange position
Assertion-Reason
Directions: Each of the questions
(i) and (ii) contain two statements – first ‘Assertion’ and second ‘Reason’. Select the correct answer to these question from the codes (a) , (b), (c) or (d) as given below:
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true and Reason is NOT the correct explanation of Assertion.
(c) Assertion is true and Reason is false.
(d) Assertion is false and Reason is true.
(i) Assertion (A): In a complete electric circuit long wire of the LED lamp is connected to negative terminal of the battery and short wire to the positive terminal of the battery. The lamp does not glow.
Reason (R): In an incandescent lamp it does not matter which of its terminals is connected to the positive or negative terminal of the cell.
(ii) Assertion (A): An electric cell is a shell of a metal having chemicals stored inside that produce electricity.
Reason (R): A cell stops working (does not supply electric current) if the chemicals stored in it are used up.
Fill in the blanks
(i) The _________ provided electricity to flow through an electric wire or a device is called the electric circuit.
(ii) _________ do not allow electric current to pass through them,
(iii) Electric energy is produced from _________ energy using wind mills.
(iv) An _________ is a portable source of electric energy.
(v) In an LED lamp the longer lead is attached to the _________ terminal of the battery.
(vi) In this image a symbol for an electric _________ in an _________ position.
(vii) Examples of _________ are items made of plastics, rubber and wood.
True or False
State whether True or False answer with reason
(i) An electric torch is a lighting device that has electric cells and a lamp.
(ii) Reflecting curved surface of the torch glows when we switch on the torch.
(iii) Copper wires covered with plastic or rubber coatings are used as conducting wires in electric wiring.
(iv) We need not differentiate between positive terminal and the negative terminal in case of incandescent lamp in a circuit.
(v) Conducting wires are connected to the terminals of the battery in a circuit without removing insulation from their ends.
(vi) A circuit diagram is a drawing of an electric circuit showing components with symbols.
Match the following
Question 1.
Match the following items given in Column A with that in Column B:
| Column A | Column B |
| 1. Long wire of an LED lamp | (a) Metal key, copper wire |
| 2. Flow of electric current in a circuit | (b) Solar panels |
| 3. Examples of insulators | (c) Battery |
| 4. Examples of conductors | (d) Positive terminal |
| 5. Solar energy | (e) Positive terminal to negative terminal of the cell |
| 6. More energy or energy for a longer time than a cell | (f) Rubber eraser, plastic scale |