Uses of electricity and staying safe
When the power goes off at night, the fan stops, the lights go out and the phone cannot be charged. That one moment shows how many jobs electricity quietly does for us every day.
Electricity is a form of energy that makes lamps glow, fans turn, and machines run. It reaches homes through wires from power stations, but for experiments we use only a cell or a battery. Mains electricity is dangerous, so students must never experiment with it. We can group uses of electricity as lighting, heating and cooling, cooking, transport, communication and entertainment.
In the figure : Electricity has many uses, but experiments must use only cells.
Rule 1: Group uses by the job done — Ask what job electricity does: light, heat, motion or sound.
- Easy : A tube light turns electricity into light.
- Medium : A geyser turns electricity into heat, and a fan turns it into motion.
- Exam-type : A doorbell turns electricity into sound, and a television gives light and sound together.
Rule 2: Safe sources only — Experiments in school use dry cells, never wall sockets.
- Easy : A single torch cell is safe for a small lamp.
- Medium : A wall socket carries far more energy and can cause a serious shock.
- Exam-type : Never touch bare wires or switches with wet hands.
Experiments need cells. Sockets are for appliances, not for students.
Thinking a small experiment with a wall socket is safe if you are careful. It is never safe for students.
Memory clue: C-N-S — Cells Nearly Safe; sockets are Not for Students.
Spot the difference
| Source | Use in class | Why |
|---|---|---|
| Dry cell | Yes | Low energy and safe |
| Battery of cells | Yes | Still safe at low strength |
| Wall socket | Never | Can cause a dangerous shock |
Practice questions
- 1Name three uses of electricity in a home.
- 2Into what form does a fan change electricity?
- 3Into what form does an electric heater change electricity?
- 4Why should students use cells and not wall sockets in experiments?
- 5Group these into light, heat or motion: lamp, iron, fan.
- 6What should you never touch with wet hands?
- 7Give two ways to group the uses of electricity.
- 8Why does a power cut stop so many things at once?
Show answers (try them yourself first)
- 1Lighting, running a fan and cooking with an induction stove (any three).
- 2Motion.
- 3Heat.
- 4Wall sockets carry high energy and can cause a dangerous shock.
- 5Lamp: light; iron: heat; fan: motion.
- 6Switches, plugs and bare wires.
- 7By the job done (light, heat, motion) or by place of use (home, school, factory).
- 8Because many devices depend on the same supply.
The electric cell and the battery
A remote control stops working, and the first thing we do is change its cells. The cells inside are small stores of electrical energy that power the device.
An electric cell is a source of electricity. It has two ends called terminals: the positive terminal (+) and the negative terminal (−). In a common torch cell, the metal cap is the positive terminal and the flat base is the negative terminal. A battery is made when two or more cells are joined together. When cells are placed in a torch, the positive end of one cell touches the negative end of the next.
In the figure : A cell has two terminals, and a battery is made by joining cells.
Rule 1: Know the two terminals — Every cell has a positive terminal and a negative terminal.
- Easy : The metal cap of a torch cell is the positive terminal.
- Medium : The flat base of that cell is the negative terminal.
- Exam-type : A circuit works only when both terminals are connected.
Rule 2: A battery is cells joined together — Two or more cells in a row make a battery.
- Easy : Two cells in a torch make a battery.
- Medium : In a battery, + of one cell touches − of the next.
- Exam-type : A battery gives a stronger push than one cell.
Cell = one source. Battery = cells joined together. Cap is +, base is −.
Thinking that a battery and a cell are always the same. A battery has more than one cell.
Memory clue: C-B-J — Cap is Plus, Base is Minus; Joined cells make a Battery.
Spot the difference
| Part | Cell | Battery |
|---|---|---|
| Number of cells | One | Two or more |
| Terminals | + and − | + at one end, − at the other |
| Push given | Smaller | Larger |
Practice questions
- 1What are the two terminals of a cell called?
- 2Which terminal is the metal cap of a torch cell?
- 3Which terminal is the flat base of a torch cell?
- 4What is a battery?
- 5How are cells placed in a torch?
- 6Why does a battery give a stronger push than one cell?
- 7A cell is put the wrong way round. What is likely to happen?
- 8Why should used cells be disposed of carefully?
Show answers (try them yourself first)
- 1Positive and negative.
- 2Positive.
- 3Negative.
- 4Two or more cells joined together.
- 5The + end of one cell touches the − end of the next.
- 6Because more cells add their push together.
- 7The torch will not work.
- 8They contain chemicals that can harm the environment.
The electric lamp
An old-style bulb glows warm and gets hot if you hold your hand near it. Inside, a very thin wire is doing the work, and it is hidden behind the glass.
An electric lamp has a thin wire called the filament enclosed in a glass bulb. When electricity passes through the filament it becomes hot and glows. This is an incandescent lamp. A lamp has two terminals. One is at the tip of the base and the other is the metal side or thread of the base. A lamp glows only when electricity passes through the filament. An LED is a newer lamp that glows without a hot filament and uses less electricity.
In the figure : A filament lamp glows when current flows through its thin wire.
Rule 1: Filament glows when current flows — The thin wire gets hot and gives light.
- Easy : In a filament lamp, the thin wire glows.
- Medium : A broken filament stops the lamp from glowing.
- Exam-type : A lamp glows only when the filament is part of a complete path for electricity.
Rule 2: Two terminals are needed — Electricity must enter at one terminal and leave from the other.
- Easy : One lamp terminal is at the tip of the base.
- Medium : The other terminal is the metal side of the base.
- Exam-type : Touching only one terminal to a cell will not light the lamp.
Filament lamp = glowing thin wire. A lamp needs both terminals connected.
Thinking that touching a lamp to just one end of a cell will make it glow. Both terminals must be connected.
Memory clue: F-T — Filament glows, Two terminals needed.
Spot the difference
| Feature | Filament lamp | LED lamp |
|---|---|---|
| Light comes from | Hot glowing wire | Special material, no hot wire |
| Gets hot | Yes | Very little |
| Electricity used | More | Less |
Practice questions
- 1What is a filament?
- 2What happens to the filament when electricity passes through it?
- 3How many terminals does a lamp have?
- 4Where are the two terminals of a filament lamp?
- 5What happens if the filament breaks?
- 6Why does a lamp glow only when connected properly?
- 7Name one advantage of an LED lamp.
- 8Why is the filament enclosed in a glass bulb?
Show answers (try them yourself first)
- 1A thin wire inside a lamp that glows.
- 2It becomes hot and glows.
- 3Two.
- 4At the tip of the base and at the metal side of the base.
- 5The lamp stops glowing.
- 6Because electricity must pass through the filament by a complete path.
- 7It uses less electricity.
- 8To protect the filament from damage.
Making a lamp glow with a cell
Take a torch apart and you will see that the lamp, the cell and the metal strip are all connected in a chain. Break the chain anywhere and the light goes out.
To make a lamp glow with a cell, connect one terminal of the lamp to one terminal of the cell, and the other terminal of the lamp to the other terminal of the cell. This forms a closed path. Wires with their plastic covering removed at the ends are used to join them. A lamp will not glow if only one terminal is connected, or if there is a gap in the path. Electricity flows from the positive terminal of the cell, through the wires and lamp, and back to the negative terminal.
In the figure : A lamp glows only when both its terminals are joined to the cell in a closed path.
Rule 1: Connect both terminals — Join each lamp terminal to a different terminal of the cell.
- Easy : One wire joins the lamp to the + of the cell.
- Medium : The second wire joins the lamp to the − of the cell.
- Exam-type : The lamp now forms part of a closed path.
Rule 2: Check the ends of wires — The plastic cover on wire ends must be removed so metal touches metal.
- Easy : Bare metal ends make a good contact.
- Medium : Loose connections can make the lamp flicker or not glow.
- Exam-type : Always check each joint if a lamp does not glow.
Lamp not glowing? Check: both terminals joined, no gaps, metal touching metal, cell good.
Joining both wires to the same terminal of the cell. This does not complete the path.
Memory clue: B-C-C — Both terminals, Closed path, Clean contacts.
Spot the difference
| Check | Good | Fault |
|---|---|---|
| Terminals joined | Two different | Same one twice |
| Wire ends | Bare metal | Covered by plastic |
| Path | Closed | Gap |
Practice questions
- 1How do you make a lamp glow using a cell and two wires?
- 2Why must the plastic cover be removed from wire ends?
- 3What is a closed path?
- 4A lamp is connected to the + terminal only. Will it glow?
- 5Name two reasons why a lamp may not glow in a simple setup.
- 6In which direction does current flow in a cell and lamp circuit?
- 7Why might a lamp flicker?
- 8What should you check first if a lamp does not glow?
Show answers (try them yourself first)
- 1Join its two terminals to the two terminals of the cell with wires.
- 2So that bare metal touches metal and electricity can pass.
- 3An unbroken path from one terminal of the cell back to the other.
- 4No, because the path is not complete.
- 5A gap in the path, or a weak or empty cell.
- 6From the positive terminal through the circuit to the negative terminal.
- 7Because of a loose connection.
- 8Whether all connections are tight and complete.
Electric circuit: closed and open
A string of festival lights sometimes goes out entirely because a single bulb has worked loose. That small gap breaks the path for the whole string.
An electric circuit is a complete path through which electricity flows. A circuit made of a cell, wires, a lamp and a switch is a simple circuit. In a closed circuit the path is complete and the lamp glows. In an open circuit there is a break in the path and the lamp does not glow. A closed circuit must include the source (cell), the connecting wires, and the device that uses electricity (the lamp).
In the figure : A closed circuit lets current flow; an open circuit stops it.
Electric circuit: closed and open
In the app you can move this figure with your finger.
Open in the appRule 1: A circuit must be a complete loop — The path from one terminal of the cell back to the other must have no gap.
- Easy : A cell, wires and a lamp in a loop form a closed circuit.
- Medium : Removing one wire makes an open circuit.
- Exam-type : A string of lights goes out if one lamp is loose, because the loop is broken.
Rule 2: Every circuit has a source and a user — The cell gives the push and the lamp uses the energy.
- Easy : The cell is the source.
- Medium : The lamp, fan or buzzer is the device that uses electricity.
- Exam-type : Wires carry electricity between them.
Closed circuit = current flows. Open circuit = no current.
Thinking electricity is used up at one end only. It flows around the loop.
Memory clue: C-O — Closed lets it Go, Open stops the Flow.
Spot the difference
| Type | Path | Lamp |
|---|---|---|
| Closed circuit | Complete | Glows |
| Open circuit | Broken | Does not glow |
| Short gap in wire | Broken | Does not glow |
Practice questions
- 1What is an electric circuit?
- 2What is a closed circuit?
- 3What is an open circuit?
- 4Name the parts of a simple circuit.
- 5What happens to the lamp in an open circuit?
- 6Why do festival lights sometimes all go out together?
- 7Which part of the circuit gives the push?
- 8Which part uses the electricity?
Show answers (try them yourself first)
- 1A complete path through which electricity flows.
- 2A circuit in which the path is complete so electricity flows.
- 3A circuit with a break so electricity cannot flow.
- 4A cell, wires and a lamp (with a switch if needed).
- 5It does not glow.
- 6A loose lamp breaks the loop.
- 7The cell.
- 8The lamp (or other device).
The electric switch
We switch on a light and the room is bright in a moment. A switch is just a neat way of closing and opening a gap in the circuit.
An electric switch is a device that closes or opens a circuit. When the switch is ON its metal strip touches both ends of the gap, so the circuit is closed and the lamp glows. When the switch is OFF the strip moves away, the gap opens and the lamp goes out. A switch can be made at home with a drawing pin, two clips and a strip of metal. In a real home, a switch is fitted on the live wire side so that the appliance is safe when it is off.
In the figure : A switch opens or closes the gap in a circuit.
Rule 1: Switch ON closes the circuit — The metal strip completes the path.
- Easy : With the switch ON, the lamp glows.
- Medium : With the switch OFF, the lamp is off.
- Exam-type : A switch works by moving a conducting strip to make or break contact.
Rule 2: Switch must be made of a conductor — The part that touches must let electricity pass.
- Easy : Metal clips make a good simple switch.
- Medium : A plastic strip would not work because it does not conduct.
- Exam-type : The base of a switch is made of an insulator for safety.
ON = closed. OFF = open. The strip must be metal.
Thinking a switch makes electricity. It only opens or closes the path.
Memory clue: O-C — ON means Closed circuit, OFF means Open circuit.
Spot the difference
| Switch position | Circuit | Lamp |
|---|---|---|
| ON | Closed | Glows |
| OFF | Open | Off |
| Strip made of plastic | Open always | Off |
Practice questions
- 1What is an electric switch?
- 2What happens when a switch is ON?
- 3What happens when a switch is OFF?
- 4What material should the strip of a simple switch be made of?
- 5Why will a plastic strip not work in a switch?
- 6What materials can be used to make a simple switch at home?
- 7Does a switch produce electricity? Explain.
- 8Why is the base of a switch made of an insulating material?
Show answers (try them yourself first)
- 1A device that closes or opens a circuit.
- 2The circuit closes and the lamp glows.
- 3The circuit opens and the lamp goes out.
- 4A metal that conducts electricity.
- 5Plastic does not conduct, so the path stays open.
- 6A drawing pin, two clips and a metal strip on a board.
- 7No, it only closes or opens the path.
- 8To keep users safe from shocks.
Circuit diagrams and symbols
Instead of drawing the full picture of a torch every time, an electrician uses a few simple signs. Like a map with symbols, a circuit diagram shows how parts are joined using small standard marks.
A circuit diagram is a simple drawing that shows how the parts of a circuit are connected using standard symbols. A cell is drawn as a long thin line and a short thick line, where the long line is the positive terminal. A battery is shown by two or more cell symbols joined. A lamp is drawn as a circle with a cross inside. A switch is drawn as a gap with a slanted line (OFF) or a joined line (ON). Wires are drawn as straight lines.
In the figure : Standard symbols let everyone read a circuit diagram in the same way.
Rule 1: Use the standard symbols — Each part has its own agreed symbol.
- Easy : A circle with a cross inside means a lamp.
- Medium : Long thin line = positive; short thick line = negative.
- Exam-type : A slanted line with a gap means an open switch.
Rule 2: Draw wires as straight lines — Show every connection clearly so the loop can be traced.
- Easy : Lines join each symbol to the next.
- Medium : The loop should start and end at the cell.
- Exam-type : A diagram with a gap shows an open circuit.
Cell: long and short lines. Lamp: circle with cross. Switch: gap or joined line.
Using the picture of a bulb instead of the lamp symbol in a diagram. Use standard symbols only.
Memory clue: L-L-S — Long line is plus, Lamp has a cross, Switch shows a gap.
Spot the difference
| Part | Symbol idea | Meaning |
|---|---|---|
| Cell | Long and short line | + and − |
| Lamp | Circle with a cross | Light source |
| Switch | Gap with slanted line | OFF, or joined line for ON |
Practice questions
- 1What is a circuit diagram?
- 2Which symbol stands for a lamp?
- 3In the cell symbol, which line is the positive terminal?
- 4How is an open switch shown?
- 5How is a battery shown in a circuit diagram?
- 6Why do we use standard symbols?
- 7Draw in words a circuit diagram of a cell, switch and lamp.
- 8What does a gap in a circuit diagram show?
Show answers (try them yourself first)
- 1A drawing of a circuit using standard symbols.
- 2A circle with a cross inside.
- 3The long thin line.
- 4As a gap with a slanted line.
- 5By two or more cell symbols joined together.
- 6So everyone can read the diagram the same way.
- 7Cell, then switch, then lamp, all joined by straight lines in a loop.
- 8An open circuit.
Conductors and insulators
An electrician's screwdriver has a metal tip and a plastic handle. The metal carries electricity where it is needed, and the plastic keeps the user safe.
A material that allows electricity to pass through it is called an electrical conductor. Metals such as copper and aluminium are good conductors. A material that does not allow electricity to pass through it is an electrical insulator. Plastic, rubber, glass, dry wood and air are insulators. To test a material, place it in a circuit between two points; if the lamp glows it is a conductor, and if it does not glow it is an insulator. Wires use a metal core to carry current and a plastic cover to stay safe.
In the figure : Conductors let electricity pass; insulators do not.
Conductors and insulators
In the app you can move this figure with your finger.
Open in the appRule 1: Test with a lamp circuit — Place the material in the gap and watch the lamp.
- Easy : With a steel spoon in the gap, the lamp glows, so steel is a conductor.
- Medium : With a rubber eraser in the gap, the lamp stays off, so rubber is an insulator.
- Exam-type : A wet cloth may let a little current pass, so always test with dry materials.
Rule 2: Use insulators for safety — Insulators protect people from shocks.
- Easy : Electricians wear rubber gloves.
- Medium : Plugs have plastic casings.
- Exam-type : Wires are covered with plastic to stop current leaking.
Metal = conductor. Plastic, rubber, glass, dry wood = insulator.
Thinking that all materials let electricity pass. Many do not, and that is why they are used for safety.
Memory clue: M-P-R — Metals Pass electricity, Plastic and Rubber Resist it.
Spot the difference
| Property | Conductor | Insulator |
|---|---|---|
| Lets electricity pass | Yes | No |
| Examples | Copper, iron | Plastic, rubber |
| Use | Wire core | Wire cover |
Practice questions
- 1What is a conductor of electricity?
- 2What is an insulator?
- 3Name three conductors.
- 4Name three insulators.
- 5How can you test whether a material is a conductor?
- 6Why are electric wires made of metal inside and plastic outside?
- 7Why do electricians wear rubber gloves?
- 8Why should materials for testing be dry?
Show answers (try them yourself first)
- 1A material that allows electricity to pass through it.
- 2A material that does not allow electricity to pass through it.
- 3Copper, aluminium, iron (any three metals).
- 4Plastic, rubber, glass (any three).
- 5Place it in a circuit gap; if the lamp glows it is a conductor.
- 6Metal carries current and plastic keeps users safe.
- 7Rubber is an insulator and protects them from shocks.
- 8Wet materials may conduct and give a wrong result.