NCERT Solutions for Class 7 Science (Curiosity) Chapter 3: Electricity: Circuits and Their Components (NCERT 2026–27)

These Class 7 Science Curiosity Chapter 3 solutions cover Electricity: Circuits and Their Components from the new NCF-2023 textbook (2026–27). Every question of the end-of-chapter exercise “Let Us Enhance Our Learning” is reproduced verbatim and solved step by step, along with key concepts, extra practice, MCQs, Assertion–Reason questions and FAQs — everything you need to master electric cells, batteries, lamps, switches, circuits and conductors.

Class: 7 Subject: Science Book: Curiosity Chapter: 3 Topic: Electricity & Circuits Session: 2026–27
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Class 7 Science Curiosity Chapter 3 Solutions – Overview

Chapter 3 of Curiosity, Electricity: Circuits and Their Components, begins with the many uses of electricity and then explores how a simple device like a torchlight works. You learn about the electric cell (a portable source of electrical energy with a positive and a negative terminal), the battery (two or more cells joined positive-to-negative), the electric lamp (incandescent lamps with a glowing filament and modern LED lamps), the electrical circuit (a complete path for current to flow), the switch (which completes or breaks a circuit), circuit diagrams drawn using standard symbols, and finally conductors and insulators. The chapter stresses safety — only batteries or cells should be used for experiments, never the mains supply, because our body is itself a conductor of electricity.

Key Concepts & Definitions

Electric cell: a portable source of electrical energy with two terminals — the metal cap is the positive (+ve) terminal and the flat metal disc is the negative (−ve) terminal.

Battery: a combination of two or more cells in which the positive terminal of one cell is joined to the negative terminal of the next. (The term “battery” is also used for a single cell, e.g. a mobile phone battery.)

Incandescent lamp: a lamp with a thin wire called a filament inside a glass bulb; the filament gets hot and glows when current passes through it. It can be connected either way round.

LED (Light Emitting Diode): a lamp with no filament and two terminals — positive (longer wire) and negative (shorter wire). Current passes through an LED in one direction only, so it must be connected the right way to glow.

Electrical circuit: a complete, closed path that allows electric current to flow. The current is taken to flow from the positive to the negative terminal of the cell.

Switch: a simple device that completes (ON / closed) or breaks (OFF / open) a circuit. In the OFF position there is an air gap between its terminals.

Circuit diagram: a representation of an electrical circuit using standard symbols for its components.

Conductors: materials (mainly metals such as copper, silver, gold) through which electric current flows easily.

Insulators: materials (plastic, rubber, glass, wood, ceramics) through which current cannot pass; they are used to cover wires, plugs and switches for safety.

“Let Us Enhance Our Learning” – NCERT Solutions

All questions below are reproduced verbatim from the NCERT Curiosity textbook (2026–27). Answers are original and exam-ready.

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) A switch is the source of electric current in a circuit — this is the incorrect statement. A switch is not a source of electric current; it only completes or breaks the circuit. The source of electrical energy in such a circuit is the electric cell or battery. Statements (ii), (iii) and (iv) are all correct.

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 an insulator is connected between A and B, because an insulator does not allow electric current to pass through it and so the circuit stays incomplete. Examples of such insulating materials are a plastic scale, a rubber eraser, a wooden stick, a glass bangle, a paper strip or a piece of wax (a candle). If, instead, a conductor such as a metal key, a coin, an iron nail or aluminium foil is connected, the lamp will glow.

3. In Fig. 3.17, if the filament of one of the lamps is broken, will the other glow? Justify your answer.

ANSWER In Fig. 3.17 the two lamps are joined one after another in the same single loop (a series arrangement), so they share one path for the current. No, the other lamp will not glow. If the filament of one lamp breaks, that lamp acts like a gap in the circuit. The circuit becomes open (incomplete), so no current can flow through any part of the loop, and the second lamp also goes off.

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. Electric wires are covered with plastic or rubber, which are insulators. If the insulating cover is not removed from the ends, the bare metal of the wire never touches the terminals of the cell and the lamp. The current cannot flow through the insulating plastic, so the circuit stays incomplete and the lamp does not glow — even though the cell and lamp are themselves fine. The covering must be removed (about 1 cm) at each end to expose the metal.

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

ANSWER A simple torch contains a battery (usually two cells), an electric lamp and a switch, all joined by wires in one closed loop. Using the standard symbols from Table 3.2, the circuit diagram is drawn as a single loop: the battery symbol (long line = positive terminal, short line = negative terminal), connected by wires to a switch, and then to the lamp, and back to the battery. A text version of the loop is shown below:
ComponentSymbol describedRole in the torch
BatteryOne long line (+) and one short line (−), drawn for two cellsSource of electrical energy
Switch (ON)A line that bridges the gap between two pointsCompletes the circuit to light the lamp
Electric lampA circle with a cross / loop insideGlows when current flows
WireA straight lineJoins all the components in a loop
Connection order (loop): Battery (+) → wire → switch → wire → lamp → wire → back to battery (−). When the switch is ON the loop is closed and the lamp glows.

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 In Fig. 3.18, switch S2 controls the path through lamp L2, while switch S1 controls the main loop that lights lamp L1. (i) S2 ON, S1 OFF → the main loop through S1 is broken, so no lamp glows (neither L1 nor L2, as current cannot leave the cell). (ii) S2 OFF, S1 ON → only the path through L1 is complete, so only L1 glows (L2 is cut off because S2 is open). (iii) Both S1 and S2 ON → both paths are complete, so both L1 and L2 glow. (iv) Both S1 and S2 OFF → the circuit is fully open, so no lamp glows.

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 Possible reasons the lamp does not glow: • The cell (or battery) is dead / discharged, or has been inserted with its terminals the wrong way for the holder. • The lamp is fused — its filament is broken, so no current can pass. • The insulating plastic cover was not removed from the ends of the connecting wires, so the metal does not make contact. • A loose connection — a wire is not tightly fixed at the cell holder, the lamp holder or the switch. • A wire is broken somewhere along its length. • The lamp is not properly screwed/fixed into its holder. • The switch terminals are not actually touching even though it looks closed (a faulty switch). How to find the fault: Check each component one by one. Replace the cell with a fresh one; test the lamp in a known working circuit; make sure 1 cm of insulation is stripped from every wire end; tighten every connection; and use a working tester (a cell and lamp with two free ends) to check that each wire and the switch actually conduct. Repairing the first faulty part found and re-testing will reveal the cause.

8. In Fig. 3.20, in which case(s) the lamp/LED will not glow when the switch is closed?

ANSWER A lamp or LED glows only when the circuit is complete and, for an LED, when it is connected the correct way round. The lamp/LED will not glow in the case(s) where the LED is connected the wrong way — that is, where the LED’s positive terminal (longer wire) is joined to the negative terminal of the battery instead of the positive. Because current passes through an LED in one direction only, a reversed LED stays off even when the switch is closed. It will also not glow in any case where the circuit is incomplete (a break, a wrong connection, or terminals not joined). An incandescent lamp, however, glows either way round as long as the loop is complete.

9. Suppose the ‘+’ and ‘−’ symbols cannot be read on a battery. Suggest a method to identify the two terminals of this battery.

ANSWER Use an LED, whose terminals are already known (longer wire = positive, shorter wire = negative). Connect the LED to the two terminals of the battery through wires and observe. If the LED glows, then the battery terminal joined to the LED’s longer (positive) wire is the positive terminal of the battery, and the other is the negative terminal. If it does not glow, interchange the connections; when it glows, identify the terminals the same way. (This works because an LED conducts in one direction only.)

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: the six cells (A, B, C, D, E, F), one torch lamp (incandescent) with a lamp holder, a cell holder, connecting wires (insulation stripped about 1 cm at the ends), and a switch (optional). (ii) Procedure: Build a simple test circuit — a cell holder joined by wires to the lamp in a lamp holder, forming a closed loop (a “cell tester”). Place one cell at a time in the holder, taking care that the negative terminal is towards the spring side, close the circuit, and observe the lamp. (iii) Carry it out: Test the cells one by one. If the lamp glows, that cell is working; if the lamp does not glow (after checking the connections are correct), that cell is not working / dead. Repeat for all six cells and note the result for each (A–F). The cells that make the lamp glow are the working ones.

11. Using an LED that 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 No, the LED will not glow as connected in Fig. 3.21. For an LED to glow, two conditions must be met: (a) the two cells must be joined in series — the positive terminal of one cell connected to the negative terminal of the next — so that they act as one battery, and (b) the LED must be connected the right way, with its longer (positive) wire to the positive terminal of the battery and its shorter (negative) wire to the negative terminal. Correct connections: First join the cells in series (+ of cell 1 to − of cell 2) to form a two-cell battery. Then connect the free positive terminal of this battery to the longer wire of the LED, and the free negative terminal to the shorter wire of the LED. With the loop closed this way, current flows in the correct direction and the LED glows.

Extra Practice Questions

Short Answer Type Questions

Q1. What is an electric cell? Name its two terminals.

ANSWERAn electric cell is a portable source of electrical energy. It has two terminals — the metal cap is the positive (+ve) terminal and the flat metal disc is the negative (−ve) terminal.

Q2. How is a battery made from cells?

ANSWERA battery is a combination of two or more cells joined so that the positive terminal of one cell is connected to the negative terminal of the next cell. This gives the circuit more energy and/or energy for a longer time.

Q3. What is the filament of an incandescent lamp and what does it do?

ANSWERThe filament is the thin wire fixed inside the glass bulb of the lamp. When electric current passes through it, the filament gets hot and glows to produce light.

Q4. Why must an LED be connected the right way in a circuit, unlike an incandescent lamp?

ANSWERCurrent passes through an LED in one direction only, so it glows only when its longer (positive) wire is joined to the positive terminal and its shorter (negative) wire to the negative terminal of the battery. An incandescent lamp glows either way because current can pass through its filament in both directions.

Q5. Why are electric wires covered with plastic or rubber?

ANSWERPlastic and rubber are insulators. The covering prevents the current from leaking out and protects people from electric shocks, since our body is itself a conductor of electricity.

Long Answer Type Questions

Q1. Explain how a switch turns a torchlight on and off. What happens to the circuit in each case?

ANSWERA switch is a simple device that either completes or breaks a circuit. In the ON position, the moving part (like the safety pin in the homemade switch) touches both terminals, closing the gap and completing the path. The circuit becomes closed, so current flows from the cell’s positive to its negative terminal and the lamp glows. In the OFF position, the moving part does not touch the second terminal, leaving an air gap. The circuit becomes open (incomplete), so no current can flow and the lamp does not glow. A switch can be placed anywhere in the circuit, and household switches work in the same way though they are designed differently.

Q2. Distinguish between conductors and insulators with examples, and explain why both are important in electrical appliances.

ANSWERConductors are materials through which electric current flows easily — chiefly metals like copper, silver and gold; copper is mostly used for wires due to its lower cost and abundant supply. Insulators (poor conductors) are materials through which current cannot pass — plastic, rubber, glass, wood and ceramics. Both are important: conductors are used for wires, switches, and the connectors of plugs and sockets so that current can flow where needed; insulators are used to cover wires, plug tops and switches so that current does not leak and people are protected from electric shocks. A safe appliance combines conducting parts to carry the current with insulating parts to keep it under control.

Q3. What is an electrical circuit? Explain the conditions under which a lamp glows, including the agreed direction of current.

ANSWERAn electrical circuit is a complete path that allows electric current to flow. A lamp glows only when one terminal of the lamp is connected to one terminal of the cell and the other terminal of the lamp to the other terminal of the cell, so that the path is complete (closed) and current passes through the filament. If the circuit is broken anywhere — by an open switch, a loose connection, a broken wire or a fused (broken) filament — no current flows and the lamp stays off. The direction of electric current in a circuit is taken to be from the positive to the negative terminal of the electric cell. For an incandescent lamp the connection can be either way round, but an LED glows only when connected in the correct direction.

Multiple Choice Questions (MCQs)

1. The metal cap of an electric cell is its:

(a) negative terminal    (b) positive terminal    (c) switch    (d) filament

2. A combination of two or more cells is called a:

(a) circuit    (b) switch    (c) battery    (d) conductor

3. In an incandescent lamp, light is produced by the glowing:

(a) glass bulb    (b) metal case    (c) filament    (d) holder

4. The longer wire of an LED is its:

(a) negative terminal    (b) positive terminal    (c) filament    (d) insulator

5. A device that completes or breaks a circuit is a:

(a) cell    (b) lamp    (c) switch    (d) battery

6. The direction of current in a circuit is taken from the:

(a) negative to positive terminal    (b) positive to negative terminal    (c) lamp to switch    (d) switch to wire

7. Which of the following is a good conductor of electricity?

(a) rubber    (b) plastic    (c) copper    (d) glass

8. Which material is an electrical insulator?

(a) iron    (b) aluminium    (c) silver    (d) plastic

9. When a switch is in the ‘OFF’ position, the circuit is said to be:

(a) closed    (b) open    (c) short    (d) complete

10. An incandescent lamp does not glow even when connected to a cell. It is most likely:

(a) too bright    (b) fused (broken filament)    (c) an LED    (d) a conductor

Answer key: 1-(b), 2-(c), 3-(c), 4-(b), 5-(c), 6-(b), 7-(c), 8-(d), 9-(b), 10-(b).

Assertion–Reason Questions

For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.

A-R 1. Assertion: An LED glows only when it is connected the correct way round in a circuit.

Reason: Electric current can pass through an LED in one direction only.

A-R 2. Assertion: A switch is the source of electric current in a circuit.

Reason: A switch only completes or breaks the circuit; the source of energy is the cell or battery.

A-R 3. Assertion: Electric wires are covered with plastic or rubber.

Reason: Plastic and rubber are insulators and protect people from electric shocks.

A-R 4. Assertion: An incandescent lamp will glow whichever way its terminals are connected to a cell.

Reason: Current can pass through the filament of an incandescent lamp in both directions as long as the circuit is complete.

A-R 5. Assertion: A fused incandescent lamp does not glow even when connected to a good cell.

Reason: A broken filament stops the flow of current through the lamp.

Answer key: 1-(A), 2-(D), 3-(A), 4-(A), 5-(A).

How to score full marks in this chapter

Remember the key rule for circuits: a lamp glows only when the circuit is complete (closed). For LED questions, always check the direction — longer wire (positive) to the positive terminal of the battery. When asked to find why a lamp does not glow, list several reasons (dead cell, fused lamp, insulation not removed, loose/broken connection, faulty switch) to get full marks. Learn the standard symbols from Table 3.2 so you can quickly draw and read circuit diagrams. State that current flows from the positive to the negative terminal of the cell.

Common mistakes to avoid

  • Calling the switch a source of current — the cell/battery is the source; the switch only opens or closes the circuit.
  • Forgetting that an LED works in one direction only — reversing it keeps it off even with the switch closed.
  • Not removing the insulating cover from the ends of wires, so no contact is made.
  • Thinking a lamp can glow in an open (incomplete) circuit — it cannot.
  • Mixing up cell terminals: the metal cap = positive, the flat metal disc = negative.
  • Performing experiments with the mains/wall supply — never do this; use only cells or batteries.

Frequently Asked Questions

What is Class 7 Science Curiosity Chapter 3 about?

Chapter 3, Electricity: Circuits and Their Components, explains how electricity is used and how a torchlight works. It covers the electric cell, battery, incandescent lamp and LED, the electrical circuit, the switch, circuit diagrams drawn with standard symbols, and conductors versus insulators, along with important electrical safety.

What is the difference between a conductor and an insulator?

Conductors, such as copper, silver and gold (mainly copper for wires), allow electric current to flow easily. Insulators, such as plastic, rubber, glass and wood, do not allow current to pass and are used to cover wires, plugs and switches to protect us from electric shocks.

Why does an LED glow only one way but a bulb glows either way?

An LED allows current to pass in one direction only, so it glows only when its longer (positive) wire is joined to the positive terminal of the battery. An incandescent lamp has a filament that current can pass through in both directions, so it glows whichever way it is connected, as long as the circuit is complete.

Are these Class 7 Science Curiosity Chapter 3 solutions free?

Yes. All solutions are free and follow the official NCERT Curiosity textbook for 2026–27.

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