iStarSign inScience 7 · Unit 9: Electricity · Cambridge Lower Secondary Science Stage 7
9.4 Conductors and insulators
15 questions · e.g. Why doesn't the painted car door conduct?
Questions
1. Which of these materials is a good conductor of electricity?
Check2. Which material could NOT be used to make electric wires?
Check3. Which material is used to make most electric wires?
Check- They are lighter than air.
- They are insulators.
- Aluminium and steel are cheaper than copper.
- They are better conductors than copper.
5. Silver is a better conductor than copper. Why are wires for home use not made from silver?
- Silver cannot be made into wires.
- Silver is not a metal.
- Silver is much more expensive than copper.
- Silver is an insulator.
6. What is an electrical conductor?
- a material that lets electrons flow through it
- a material that stops electrons flowing
- a material that stores electrons
- a material that makes electrons
7. What is an electrical insulator?
- any metal
- a material that lets electrons flow easily
- a material that stops electrons flowing through it
- a material that makes electricity
8. Which of these is an insulator?
Check9. Why are electric wires covered in plastic?
- Plastic is a conductor.
- Plastic makes the current bigger.
- Plastic keeps the electrons warm.
- Plastic is an insulator, so it stops current reaching you.
10. Plastic insulation on wires keeps people safe. What is another use of the plastic insulation?
- It stores electrons.
- It makes the current flow faster.
- It can be coloured differently to identify each wire.
- It makes the wire a better conductor.
11. Power lines hang from metal pylons on insulators. Why are the insulators needed?
- They hold extra electrons.
- They stop current flowing from the wires into the metal pylon.
- They keep the wires warm.
- They make the wires conduct better.
12. Zara touches her circuit's metal contacts to a large piece of iron, and the lamp lights. Why?
- Iron gives out light.
- Iron stores electricity.
- Iron is an insulator.
- Iron is a metal, so it conducts electricity and completes the circuit.
13. A car is made of steel, but the lamp does not light when Zara touches the car door. Why?
- The door is covered in paint, which is an insulator.
- Steel is an insulator.
- Cars have no electrons.
- The car is too big.
14. How could Zara get the lamp to light using the car?
- Touch the contacts to the tyres.
- Touch the contacts to bare metal, where there is no paint.
- Press harder on the paint.
- Touch the contacts to the window.
- Gold has free electrons that can move, but in glass the electrons cannot move.
- Glass has no electrons.
- Gold has no electrons.
- Glass has more free electrons than gold.