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Electric Circuits — Answers

Answer sheet with model answers and success criteria for the Year 7 energy, light, sound & electricity worksheet.

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Success TutoringWorksheetsAnswer sheetYear 7 · Science · Energy, Light, Sound & Electricity

Electric Circuits — Answers

Part A: How circuits work

Read the passage. Then circle the best answer.

An electric circuit is a path that electricity flows around. A simple circuit can have a battery (the energy source), wires, a bulb and a switch.

Electricity can only flow if the circuit is complete — a closed loop with no gaps. If there is a gap anywhere, the circuit is broken and the bulb will not light.

A switch is a way of making or breaking a gap. When the switch is closed (on), the loop is complete. When it is open (off), there is a gap.

Conductors let electricity flow through them easily. Metals such as copper, iron and steel are good conductors. Insulators do not let electricity flow through them easily. Plastic, rubber, wood and glass are insulators.

1.Why does a bulb light up in a complete circuit?
  1. AThe wires are long.
  2. BElectricity can flow all the way around the loop.
  3. CThe battery is touching the bulb.
  4. DThe switch is open.

Answer: Electricity can flow all the way around the loop.

In a complete (closed) circuit there are no gaps, so electricity flows from the battery, through the bulb and back to the battery.

2.Which material is a good conductor of electricity?
  1. Acopper
  2. Bplastic
  3. Crubber
  4. Dwood

Answer: copper

Metals such as copper are good conductors. That is why wires have copper inside.

3.What happens when you open (turn off) a switch?
  1. AThe bulb gets brighter.
  2. BThe battery charges.
  3. CIt makes a gap, so the circuit is broken and the bulb goes out.
  4. DElectricity flows faster.

Answer: It makes a gap, so the circuit is broken and the bulb goes out.

Opening the switch breaks the loop. With a gap in the circuit, electricity cannot flow.

4.Why are electrical wires covered in plastic?
  1. Ato make them heavier
  2. Bto make them conduct better
  3. Cto make them look colourful
  4. Dbecause plastic is an insulator and keeps us safe

Answer: because plastic is an insulator and keeps us safe

Plastic is an insulator: it does not let electricity pass through, so the covering stops electricity reaching our hands.

Part B: Parts and words

5.Match each circuit part to its job.
  • battery
  • wire
  • bulb
  • switch
  • turns electrical energy into light
  • opens or closes a gap in the circuit
  • supplies the energy
  • carries electricity around the circuit

Answer: battery → supplies the energy; wire → carries electricity around the circuit; bulb → turns electrical energy into light; switch → opens or closes a gap in the circuit

6.A circuit with no gaps is called a (answer space) circuit.

Answer: complete

Also accept: closed.

7.Materials that do not let electricity flow easily are called (answer space).

Answer: insulators

Part C: True or false?

Write True or False.

8.A steel paper clip is a conductor.

Answer: True

Steel is a metal, and metals conduct electricity.

9.A rubber band would let electricity flow through a circuit.

Answer: False

Rubber is an insulator, so it would act like a gap.

10.It is safe to touch switches or plugs with wet hands.

Answer: False

Water can carry electricity. Always dry your hands before touching anything electrical.

11.You should never poke objects into the places where plugs go in the wall.

Answer: True

Electricity from the wall is very powerful and can seriously hurt you.

12.A bulb will light even if one wire is not connected.

Answer: False

The loose wire leaves a gap, so the circuit is not complete.

Part D: Working scientifically: conductor or insulator?

Only build circuits at school with a teacher, using small batteries. Never experiment with electricity from the wall.

In class, a group builds a circuit with a battery, a bulb and wires, leaving a small gap. They put different materials across the gap, one at a time, to see whether the bulb lights.

13.What is the one thing the class changes each time?

Answer: The material put in the gap.

14.How will they know if a material is a conductor?

Answer: The bulb lights up when the material is in the gap.

15.Name two things they must keep the same.

Answer: Any two of: the same battery, the same bulb, the same wires, the same size gap, connecting the materials the same way.

16.Predict which of these will make the bulb light: a metal spoon, a plastic ruler, a wooden block, aluminium foil, a rubber eraser. Explain your prediction.

Model answer: The metal spoon and the aluminium foil will make the bulb light, because they are metals and metals are conductors. The plastic ruler, the wooden block and the rubber eraser will not, because they are insulators.

Success criteria:

  • Predicts the spoon and foil conduct
  • Predicts plastic, wood and rubber do not
  • Explains using conductors (metals) and insulators
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