Complete Summary and Explanation of Electricity: Circuits and their Components – Curiosity/NCRT Class 7 Science Chapter 3 – Full Chapter Notes, Torchlight Activity, Uses of Electricity, Safety Rules, Components, and Solutions

Full Chapter Summary & Detailed Notes

Overview

This chapter introduces electric cells and batteries, lamps (incandescent and LED), electric circuits, switches, circuit diagrams, and the difference between conductors and insulators. It explains how a torch works and gives simple activities to understand circuit construction and testing.

Context & Story

Nihal's school trip to Bhakra Nangal Dam and the group's assignment to list uses of electricity set the stage for this chapter. They discover many real-life applications (lighting, communication, heating/cooling, transport) and then focus on portable sources like cells and batteries. (Content source: Chapter 3 PDF). :contentReference[oaicite:2]{index=2}

Key Sections

A torchlight: Components inside—cells, lamp, switch. How changing the switch position makes the lamp glow or not.
Electric cell & battery: Positive and negative terminals; connecting cells in series to make a battery.
Lamps: Incandescent lamp (filament) and LED (directional current; longer lead = positive).
Making a lamp glow: How to connect lamp, cell(s) and wires to complete a circuit.
Switches: How a simple switch completes or breaks a circuit (ON/OFF positions).
Circuit diagrams: Symbols for cells, battery, lamps, LED, switch and wires.
Conductors & insulators: Metals conduct electricity; plastics, rubber and ceramics are insulators.

Fig. 3.1 – A Torchlight

Typical torch contains two or more cells, a lamp (incandescent or LED), and a switch. Cells provide portable electric energy to the lamp when the circuit is complete.

In a nutshell:

An electric cell is a portable source of electrical energy having two terminals: + (positive) and − (negative).
Incandescent lamp glows when current passes through its filament; LED glows only if connected in correct direction (longer lead → positive).
A complete path (circuit) is required for current flow; switches open/close the circuit.
Metals are good conductors; rubber, plastic, glass are insulators. Safety caution: never experiment with mains supply — use cells for experiments. :contentReference[oaicite:3]{index=3}

Key Definitions & Terms

Electric cell

A portable source of electrical energy with two terminals (+ and −). Example: torch cell.

Battery

Combination of two or more cells connected in series to provide longer life or higher voltage.

Incandescent lamp

A lamp with a filament that gets hot and glows when current passes through it.

LED (Light Emitting Diode)

A diode that emits light when current passes in one direction; has a longer lead (positive) and shorter lead (negative).

Electric circuit

A complete path through which electric current can flow.

Switch

A device that completes (ON) or breaks (OFF) an electrical circuit.

Conductor

Material that allows electric current to pass through easily (e.g., copper, aluminium).

Insulator

Material that prevents the flow of electric current (e.g., rubber, plastic, glass).

Filament

The thin wire inside an incandescent lamp that glows when heated by current.

Terminal

The point of connection on a cell, lamp, or battery (marked + and −).

Tip: Keep this glossary handy while doing activities and drawing circuit diagrams.

Activities & Observations (from the textbook)

Activity 3.1 – Exploring a Torchlight

What to do

Take a torch, observe the lamp and switch.
Slide the switch — note whether the lamp glows or goes off.
Open the torch and observe cells inside — their arrangement matters for the lamp to glow.

Activity 3.2 – Observe an Electric Cell

What to do

Look for + and − signs, the protruding metal cap (positive) and flat metal disc (negative).
Discuss why the cell is a portable source of electrical energy.

Activity 3.3 – Making a Battery

What to do

Use two or more cells; place them so positive of one connects to negative of the next (series connection).
Observe lamp glow with cells placed correctly vs reversed.

Activity 3.6 – Construct a Simple Circuit

Materials

Electric cell, incandescent lamp, cell holder, lamp holder, wires.

Procedure & Observations

Strip wire ends, connect cell to lamp via wires and holders (or tape if holders not present).
Predict whether lamp will glow in different arrangements; observe and fill Table 3.1.
Only arrangements with a complete path (circuit) allow current to flow and lamp to glow. (See textbook examples). :contentReference[oaicite:4]{index=4}

Activity 3.7 – Making an LED Glow

Use two cells in holder, connect longer LED lead to battery +, shorter to battery −.
LED glows only when connected in correct polarity. If reversed, it will not light.

Activity 3.8 & 3.9 – Make a Simple Switch

Use drawing pins and a safety pin mounted on cardboard to make a rotating switch.
Connect it in a circuit; touching the drawing pins closes the circuit (ON), separating opens it (OFF).

Key Concepts — Quick Reference

Series Connection

Cells placed positive to negative increase total voltage (useful to power devices requiring higher voltage).

Polarity & LED

LED is direction-sensitive: positive lead (longer) must connect to positive terminal of battery.

Complete vs Open Circuit

A complete (closed) circuit allows current flow and devices glow; an open circuit prevents flow.

Switch Function

Switches complete or break circuits and can be placed anywhere in the circuit.

Conductors vs Insulators

Conductors (metals) carry current; insulators (rubber/plastic/ceramic) prevent current and provide safety.

Fused Lamp

A filament that is broken prevents current flow — the lamp 'fuses' and does not glow.

Tip: When troubleshooting, check arrangements, loose connections, fused filament, and cell orientation.

Circuit Diagrams & Symbols

Use standard symbols to draw circuit diagrams — they make representation simpler and universal.

Component	Symbol	Notes
Electric Cell	Long line ( + ) and short line ( - )	Long = positive terminal
Battery	Multiple cell symbols in series	Shows combined voltage
Electric Lamp (incandescent)	Circle with filament or simple bulb icon	Filament glows when current flows
LED	Triangle with line + arrows	Direction matters; arrows indicate light emission
Switch (ON/OFF)	Break in line with movable contact	Opens/closes circuit
Wire	Line	Connects components

Fig. 3.14 – Circuit Diagrams

Examples: (a) incandescent lamp circuit diagram (b) LED circuit diagram — use symbols to draw the circuits you build.

Conductors and Insulators

Explore different materials to identify conductors and insulators using a simple conduction tester (cell + lamp + wires).

Activity 3.11 – Identify Materials

Materials to test

Metal spoon, coin, key, pin, aluminium foil (expected: conductor)
Wood, rubber, plastic scale, cork, glass, paper (expected: insulator)
Test and note whether lamp glows (Yes = conductor, No = insulator).

S.No.	Object	Material	Lamp Glows?	Conclusion
1	Spoon	Metal	Yes	Conductor
2	Plastic scale	Plastic	No	Insulator
3	Glass	Glass	No	Insulator
4	Key	Metal	Yes	Conductor

Why use metals? Metals (silver, copper, gold) are excellent conductors; copper is commonly used due to availability and cost. Insulators protect us from shocks — why wires are covered by plastic or rubber.

Examples & Step-by-step Explanations

Example 1 — Will the lamp glow?

Scenario: Lamp connected to a single cell with wires completing a closed loop.

Answer: Lamp will glow because circuit is complete and current flows through filament (if filament intact).

Example 2 — LED not glowing

Scenario: LED is connected but not glowing after swapping wires.

Answer: Check LED polarity — LED lights only when anode (longer lead) is connected to + and cathode to −. Also check cells and connections.

Example 3 — Fused lamp

Scenario: Lamp doesn't glow despite correct circuit.

Answer: Filament might be broken (fused). Replace lamp and retry.

Interactive Quiz – Master Electricity Concepts

Test yourself with 10 MCQs based on Class 7 Chapter 3

Quick Revision Notes

Topic	Key Points	Example
Cell	Portable electrical source; + and − terminals	Torch cell
Battery	Series connection of cells; higher voltage	Two cells in torch
Lamp (Incandescent)	Filament glows when current flows	Old torch bulbs
LED	Direction-sensitive; long lead = +	Modern torch LEDs
Switch	Completes or breaks circuit	Wall switch/torch switch

Revision tip: When in doubt, redraw the circuit using symbols and check continuity and polarity step-by-step.

Let Us Enhance Our Learning — Full Practice Questions with Solutions

A. Very Short Answer Questions (1 Mark)

1. What are the two terminals of an electric cell?

Positive terminal (+) and Negative terminal (−).

2. What glows inside an incandescent bulb?

The filament.

3. Does an LED glow in both directions?

No. It glows only in the correct direction (polarity matters).

4. What does a switch do?

It makes or breaks an electric circuit.

5. Name one conductor and one insulator.

Conductor: Copper | Insulator: Plastic

B. Short Answer Questions (2–3 Marks)

6. Why does a fused bulb not glow?

Because its filament is broken. This breaks the circuit and stops current flow.

7. Why must cells be connected the correct way?

Cells must be connected positive-to-negative (series). Wrong connection → no effective voltage → device won’t work.

8. Why are wires covered with plastic?

Plastic is an insulator — it prevents electric shocks and makes handling safe.

9. How do we identify the positive terminal of a cell?

The metal cap is the positive terminal.

10. What is an open circuit?

A circuit in which there is a gap, preventing current flow.

C. Long Answer Questions (4–5 Marks)

11. Differentiate between conductor and insulator.

Conductor	Insulator
Allows current to pass	Does not allow current
Copper, aluminium	Plastic, rubber, wood
Used in wires	Used for covering wires

12. Explain how a torch works.

Cells supply electricity.
Switch completes or breaks the circuit.
When the switch is ON → current flows → lamp glows.
When OFF → circuit breaks → lamp stops glowing.

13. Explain how to make a simple switch at home.

Fix two drawing pins on cardboard.
Attach a safety pin to one of them.
Connect wires to both pins.
Touching pins → circuit closes (ON)
Not touching → circuit opens (OFF)

D. Multiple Choice Questions

14. LED glows only when:

Connected in any direction
Connected in the correct direction
Connected without a cell
Connected to fuse

Correct Answer: B

15. Which of these is an insulator?

Aluminium
Copper
Plastic
Iron

Correct Answer: C

16. Which arrangement will make a bulb glow?

Open circuit
Closed circuit
Reversed cell with no wires
Only bulb with no cell

Correct Answer: B

E. True / False

17. A battery is made of two or more cells.

True

18. A fused bulb glows brightly.

False

19. Rubber is a conductor.

False

F. Diagram-Based Questions

20. Draw symbols of cell, battery, lamp, switch.

✔ Cell → long & short line
✔ Battery → repeated cell symbols
✔ Lamp → circle with filament
✔ Switch → break in line

21. A bulb doesn't glow even after connection. Give reasons.

Filament is broken (fused).
Cell is dead.
Loose connections.
Reversed polarity.
Wire is broken.

G. Application-Based Questions

22. Why is aluminium used in overhead cables?

It is a good conductor, lightweight, and cheaper than copper.

23. Why are LED bulbs more efficient?

Use very little energy
Do not heat up
Long life
Directional current makes them efficient

H. Higher Order Thinking Skills (HOTS)

24. Will an LED glow if connected in reverse?

No. LED glows only in one direction (polarity sensitive).

25. Why is copper used in house wiring?

It is a very good conductor, low resistance, does not rust, and is safe.

26. A boy connects two cells but bulb doesn’t glow. Why?

Dead cell
Wrong polarity
Loose connection
Broken wire
Fused bulb

I. Fill in the Blanks

27. The glowing part of a bulb is called ______.

Filament

28. A material that allows current is a ______.

Conductor

29. A gap in a circuit makes it ______.

Open

J. Assertion–Reason Questions

30. Assertion: A fused bulb does not glow.
Reason: Its filament is broken.

Both are true; Reason correctly explains Assertion.

31. Assertion: Screwdrivers have plastic handles.
Reason: Plastic is an insulator.

Both statements are true and reason explains the assertion.

K. Advanced Questions

32. You have one cell but need more brightness. What to do?

Use two cells in series to form a battery.

33. What happens if you add more cells?

Brightness increases (but too many may fuse the bulb).

34. Why should we NOT use household electricity for experiments?

Mains electricity is dangerous (high voltage) — can cause shocks. Use only cells.

Complete Summary and Explanation of Electricity: Circuits and their Components – Curiosity/NCRT Class 7 Science Chapter 3 – Full Chapter Notes, Torchlight Activity, Uses of Electricity, Safety Rules, Components, and Solutions

Electricity: Circuits and Components

Full Chapter Summary & Detailed Notes

Overview

Context & Story

Key Sections

Fig. 3.1 – A Torchlight

Key Definitions & Terms

Electric cell

Battery

Incandescent lamp

LED (Light Emitting Diode)

Electric circuit

Switch

Conductor

Insulator

Filament

Terminal

Activities & Observations (from the textbook)

Activity 3.1 – Exploring a Torchlight

What to do

Activity 3.2 – Observe an Electric Cell

What to do

Activity 3.3 – Making a Battery

What to do

Activity 3.6 – Construct a Simple Circuit

Materials

Procedure & Observations

Activity 3.7 – Making an LED Glow

Activity 3.8 & 3.9 – Make a Simple Switch

Key Concepts — Quick Reference

Series Connection

Polarity & LED

Complete vs Open Circuit

Switch Function

Conductors vs Insulators

Fused Lamp

Circuit Diagrams & Symbols

Fig. 3.14 – Circuit Diagrams

Conductors and Insulators

Activity 3.11 – Identify Materials

Materials to test

Examples & Step-by-step Explanations

Example 1 — Will the lamp glow?

Example 2 — LED not glowing

Example 3 — Fused lamp

Interactive Quiz – Master Electricity Concepts

Quick Revision Notes

Let Us Enhance Our Learning — Full Practice Questions with Solutions

A. Very Short Answer Questions (1 Mark)

1. What are the two terminals of an electric cell?

2. What glows inside an incandescent bulb?

3. Does an LED glow in both directions?

4. What does a switch do?

5. Name one conductor and one insulator.

B. Short Answer Questions (2–3 Marks)

6. Why does a fused bulb not glow?

7. Why must cells be connected the correct way?

8. Why are wires covered with plastic?

9. How do we identify the positive terminal of a cell?

10. What is an open circuit?

C. Long Answer Questions (4–5 Marks)

11. Differentiate between conductor and insulator.

12. Explain how a torch works.

13. Explain how to make a simple switch at home.

D. Multiple Choice Questions

14. LED glows only when:

15. Which of these is an insulator?

16. Which arrangement will make a bulb glow?

E. True / False

17. A battery is made of two or more cells.

18. A fused bulb glows brightly.

19. Rubber is a conductor.

F. Diagram-Based Questions

20. Draw symbols of cell, battery, lamp, switch.

21. A bulb doesn't glow even after connection. Give reasons.

G. Application-Based Questions

22. Why is aluminium used in overhead cables?

23. Why are LED bulbs more efficient?

H. Higher Order Thinking Skills (HOTS)

30. Assertion: A fused bulb does not glow.
Reason: Its filament is broken.

31. Assertion: Screwdrivers have plastic handles.
Reason: Plastic is an insulator.