Topic 6 of 8 · Grade 7
Electricity and magnetism
Cell, battery, bulb, switch (open and closed), wire.
Notes for this topic 1 file, in order
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Electricity
- A simple circuit needs a source (cell or battery), wires and a component such as a bulb; a switch opens and closes the circuit.
- Conductors allow electricity to flow (copper, iron, aluminium); insulators do not (plastic, rubber, wood, glass).
- Series circuits: one path; if one bulb breaks, all go out. Parallel circuits: several paths.
Circuit symbols
Cell, battery, bulb, switch (open and closed), wire.
Electrical safety
Do not touch switches with wet hands, do not overload sockets, never play near power lines, do not put objects into sockets, and report damaged cables. Lightning safety: stay indoors, avoid tall trees and open fields.
Magnetism
Magnets attract iron, steel, nickel and cobalt. Every magnet has a north and a south pole: like poles repel, unlike poles attract. A compass needle is a magnet that points north. Uses: compasses, fridge doors, electric motors, speakers.
Worked example: A bulb in a circuit does not light. Give two possible reasons.
The switch is open; the bulb is broken; a wire is loose; or the cell is flat.
Check yourself
- Name two good conductors of electricity.
- What happens when two north poles are brought together?
- Why should you not touch switches with wet hands?
Show answers
- Any two: copper, iron, aluminium, steel, silver.
- They repel each other.
- Water conducts electricity, so you could get an electric shock.
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