Alternating current and direct current
4 marks · NormalA mobile phone charger is rated at 5 V and is connected to a current of 0.6 A.
Calculate the power used by the charger.
If the charger is used for 3 hours, calculate the total energy transferred in kilojoules (kJ).
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) 3.0 W
(b) 32.4 kJ
Common mistakes: Not converting hours to seconds; giving final energy in J not kJ
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Power calculated as .
M2 (b) · 1 mark · Convert 3 hours to 10800 seconds.
M3 (b) · 1 mark · Energy calculated as . Allow FT from (a). (follow-through)
A1 (b) · 1 mark · Energy converted to kJ, correctly rounded (32.4 kJ). (follow-through)
Worked solution
(a) W
(b) hours = s, J = 32.4 kJ