NCERT Solutions for Class 7th Science Chapter 3 Electricity: Circuits and their Components
Updated on 2026-09-19
About this chapter
An electric cell is a portable source of electrical energy. Its metal cap is the positive (+) terminal and its flat metal disc is the negative (–) terminal. Two or more cells joined so that the + terminal of one touches the – terminal of the next make a battery. A battery gives energy for a longer time and/or more energy. An incandescent lamp glows because current heats its thin filament. An LED has no filament, and current can pass through it in one direction only — its longer wire is the + terminal. A lamp glows only when the circuit is complete, that is, when one terminal of the lamp is joined to one terminal of the cell and the other to the other terminal. The direction of current is taken from + to – of the cell. A switch simply completes (ON, closed circuit) or breaks (OFF, open circ
- Chapter opener and A Torchlight
- A Torchlight
- Electric cell
- Battery
- Electric lamp
- An electrical circuit
- Electric switch
- Circuit Diagrams
- Electrical Conductors and Insulators
- End-of-chapter questions
Quick revision
| Term | What it means | Key point to remember | Example from the chapter |
|---|---|---|---|
| Electric cell | A portable source of electrical energy with two terminals | Metal cap = positive (+), flat metal disc = negative (–) | The cell in a wall clock or a torch |
| Battery | Two or more cells joined + of one to – of the next | Gives energy for longer and/or more energy | Fig. 3.3 — battery of two cells, battery of four cells |
| Terminal | One of the two ends of a cell, lamp or LED | Terminals must not touch each other | + and – marked on every cell |
| Filament | The thin wire fixed inside the glass bulb of a lamp | It gets hot and glows to give light | Torch bulb in Fig. 3.4a |
| Incandescent lamp | Lamp that lights up because its filament gets hot | Works whichever way round it is joined | Old torch bulb |
| LED | Light Emitting Diode — a lamp with no filament | Current passes one way only; longer wire = + terminal | Coloured LEDs in Fig. 3.6 |
| Electrical circuit | A complete path for electric current to flow | The lamp glows only when the path is complete | Fig. 3.9 |
| Direction of current | Taken to be from the + terminal to the – terminal of the cell | This is the agreed direction in the outside circuit | Fig. 3.12b, switch ON |
| Switch | A simple device that completes or breaks a circuit | ON = circuit closed; OFF = circuit open (air gap) | Safety-pin and drawing-pin switch, Fig. 3.11 |
| Circuit diagram | A picture of a circuit drawn with standard symbols | Long line = + terminal, short line = – terminal | Fig. 3.14a and Fig. 3.14b |
| Conductor | Material through which electric current flows easily | All metals; copper is used for wires as it is cheap and plentiful | Key, coin, aluminium foil, pencil lead |
| Insulator | Material through which current cannot pass | Used to cover wires, plug tops and switches for safety | Rubber, plastic, glass, wood, wax, ceramics |
Exercises
- Chapter opener and A Torchlight — In-text Questions Page 24
- Activity 3.1: Let us explore — A Torchlight Page 24
- Activity 3.2: Let us observe — Electric cell Page 25
- In-text Questions — Battery Page 25
- Activity 3.3: Let us experiment — Battery Page 25
- Activity 3.4: Let us observe — Electric lamp Page 26
- Activity 3.5: Let us observe — Electric lamp Page 27
- Activity 3.6: Let us construct — Making an electric lamp glow using an electric cell or battery Page 28
- In-text Questions — An electrical circuit Page 30
- Activity 3.7: Let us experiment — An electrical circuit Page 31
- Dive Deeper — An electrical circuit Page 31
- In-text Questions — Electric switch Page 32
- Activity 3.9: Let us test — Electric switch Page 32
- In-text Questions — Circuit Diagrams Page 33
- Activity 3.10: Let us draw — Circuit Diagrams Page 34
- In-text Questions — Electrical Conductors and Insulators Page 34
- In-text Questions — Electrical Conductors and Insulators Page 35
- Activity 3.11: Let us identify — Electrical Conductors and Insulators Page 35
- In-text Questions — Electrical Conductors and Insulators Page 36
- End-of-chapter questions — Let Us Enhance Our Learning Page 37–39
- Interdisciplinary — Exploratory Projects Page 39–40