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Specific Heat Capacity and Latent Heat Questions - GCSE standard

Q5. The plug of an electrical appliance contains a fuse. The diagram shows the structure of a fuse.

(a) Which of the following is the correct circuit symbol for a fuse?

Choice B

[1 mark]

(b) The appliance is connected to the mains electrical supply.

The mains potential difference is 230 V.

Calculate the energy transferred when 13 C of charge flows through the appliance.

P = IV

but

P = E/t and I = Q/t

so

E = QV

E = 13 x 230

E = 2990 J

[3 marks]

(c)

(i) Write down the equation that links charge flow, current and time.

Q = It

[1 mark]

(ii) The fuse wire melts when 1.52 coulombs of charge flows through the fuse in 0.40 seconds. Calculate the current at which the fuse wire melts.

I = Q/t

I = 1.52/0.4

I = 3.8A

[3 marks]

(d) The mass of the fuse wire is 0.00175 kg.

The specific latent heat of fusion of the fuse wire is 205 000 J/kg.

Calculate the energy needed to melt the fuse wire.

E = mL

E = 0.00175 x 205000 = 358.75 J

Note that the unit for the specific latent heat of fusion give a big clue of the equation linking energy and mass!

[3 marks]

(Total 10 marks)