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Question 3

An electric microwave oven is connected to the 230 V230\text{ V}230 V mains supply. The power of the microwave is 1400 W1400\text{ W}1400 W.

a.

A power of 1400 W1400\text{ W}1400 W is equivalent to:

  • A 1400 joules per coulomb1400\text{ joules per coulomb}1400 joules per coulomb
  • B 1400 joules per second1400\text{ joules per second}1400 joules per second
  • C 1400 newtons per metre1400\text{ newtons per metre}1400 newtons per metre
  • D 1400 newtons per second1400\text{ newtons per second}1400 newtons per second
[1]
b.

State the equation linking power, current, and voltage.

[1]
c.

Show that the current in the microwave oven is approximately 6 A6\text{ A}6 A.

[2]
d.

The microwave is earthed and fitted with a fuse. Explain how the earth wire and fuse protect the user if a fault occurs where the live wire contacts the metal casing.

[3]
e.

A commercial microwave oven has twice the power rating of this model. It is connected to the same 230 V230\text{ V}230 V mains supply. Which of the following fuse ratings is most suitable for this commercial microwave?

  • A 3 A3\text{ A}3 A
  • B 5 A5\text{ A}5 A
  • C 10 A10\text{ A}10 A
  • D 13 A13\text{ A}13 A
[1]
f.

A student has a pack of fuses labelled 5 A5\text{ A}5 A. Explain how they could safely test one of these fuses in a school laboratory to check that the 5 A5\text{ A}5 A rating is correct.

[3]
Markscheme

Electricity Questions

  1. IGCSE
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