Units (Electricity)
4 marks · EasyThe information panel on an electric toaster says: 'Power: 800 W, Voltage: 200 V'. The plug has a fuse fitted.
Calculate the current drawn by the toaster when it is working.
Suggest which fuse should be used in the plug if the available sizes are 3 A and 5 A. Explain your answer.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) 4.0 A
(b) 5 A fuse; because the current is 4 A, the next suitable fuse size above this is 5 A, which will protect the appliance without blowing unnecessarily. · must show choice justified using calculation and safety
Common mistakes: Dividing voltage by power; Selecting a fuse that matches the exact current and not the next size up
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Marking points
M1 (a) · 1 mark · Substitutes in P = I × V or rearranged to I = P / V.
A1 (a) · 1 mark · Arrives at correct value I = 4.0 A (with clear unit).
B1 (b) · 1 mark · Chooses correct fuse (5 A).
B2 (b) · 1 mark · Explains why 5 A fuse is suitable; i.e., next size above.
Worked solution
a) Power, P = 800 W; Voltage, V = 200 V. Use the equation:
b) The toaster current is 4.0 A. The next available fuse size above 4.0 A is 5 A. A 3 A fuse would blow because it is lower than the normal working current.