Electricity
5 marks · NormalA kettle is marked '230 V, 1800 W'.
Calculate the current flowing through the kettle.
State and justify which of the following fuses is most appropriate for this kettle: 3 A, 5 A, or 13 A.
Explain the effect of resistance in the heating element of the kettle.
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.
Show answer
(a) 7.83 A
(b) A 13 A fuse, as it is the next size above 7.83 A and will prevent overheating due to excessive current.
(c) The resistance in the heating element causes electrical energy to be transferred to thermal energy, heating the water.
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Uses I = P / V.
A1 (a) · 1 mark · Accurate: 7.83 A. (follow-through)
B1 (b) · 1 mark · Selects the correct fuse value (13 A).
B2 (b) · 1 mark · Gives a reason for choosing fuse size (next size up, safety).
B3 (c) · 1 mark · Explains heating effect of resistance in element.
Worked solution
b. The fuse must be slightly higher than 7.83 A, so 13 A is correct. 3 A and 5 A would melt during normal use.
c. Resistance in the element causes energy transfer as heat (I^2R), so the water boils.