The plastic coating on electrical wires is an insulator.

# Electrical Circuits 02

Test yourself on electrical circuits in this KS3 Science quiz. Insulators and conductors are words used in relation to electrical circuits. An insulator is a substance that does not allow electricity to pass through. It is useful for making sure that electricity does not get to places where it should not be! Examples of materials that are insulators are plastics and ceramics. Plastics are flexible and can be used on the outside of electrical wires, which need to be able to bend. Ceramics are brittle and inflexible. They are used on electricity pylons to keep the high voltage lines from touching the pylon. Metals are good conductors of electricity, some are better than others. Copper is a much better conductor than steel and is more malleable (bendy) so is a good choice for making wires. But copper is too heavy and weak to use for the large overhead wires that are used to transfer electricity around the countryside so aluminium is used instead.

Components in an electrical circuit can be joined in two ways, series or parallel. In series, they are one after the other (like a TV series, each episode comes after the previous one). If one component in a series circuit breaks, the whole circuit stops working. In a parallel circuit, if one breaks, the rest of the circuit still works.

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1. Two bulbs are in series in a complete circuit. If the voltage is increased:
The number of bulbs was not changed so there is more current flowing and the bulbs are brighter
2. Three identical bulbs are in parallel in a complete circuit. The current in each bulb:
The current in each bulb is a third of the total current flowing round the circuit
3. Which of the following statements is true?
If the four bulbs were NOT identical, the current would still be shared out, but not equally
4. Which of the following statements is true?
It can sometimes be helpful to think of electricity flowing round a circuit like water through pipes
5. If the size of a battery in a complete circuit is increased:
An increase in voltage will increase the current flowing in a circuit (if nothing else is changed)
6. Two identical bulbs are in parallel in a complete circuit. A third identical bulb is connected in parallel. What happens?
Adding identical bulbs in parallel uses more current but brightness stays the same
7. Wires are normally made from copper. This is because:
It is also very malleable and can therefore easily be bent to go round corners
8. Wires are usually coated in plastic because:
Wires used to be covered with rubber as an insulator but rubber perishes faster than plastic
9. The current in a series circuit containing two bulbs:
This is an important point to remember about a series circuit
10. Two identical bulbs are in parallel in a complete circuit. If one breaks:
This is a benefit of a parallel circuit, it is usually easier to find out which component has broken as the rest still work

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