Mains Electricity
4 marks · NormalA 800 W microwave oven is used in a home where the mains supply is 240 V.
Calculate the current taken by the oven.
The oven is used for 2 minutes. Calculate the total energy transferred by the oven during this time.
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) 3.33 A
(b) 96000 J
Common mistakes: Incorrect unit conversion for time; Incorrect formula rearrangement
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Uses correct equation: P = I × V, rearranged to I = P/V
A1 (a) · 1 mark · Accurate final answer (3.33 A)
M2 (b) · 1 mark · Energy calculated with E = P × t, time in seconds
A2 (b) · 1 mark · Correct evaluation: 800 × 120 = 96000 J
Worked solution
a)
b) Time = 2 minutes = 2 × 60 = 120 s. Energy