Alternating current and direct current

3 marks · Normal

A 150 W computer monitor runs on a 19 V supply. Calculate the current in the monitor and the total energy transferred if it is used for 2 hours.

(a)

Calculate the current. Give your answer to 2 decimal places.

[2 marks]

(b)

Calculate the energy transferred in kilojoules (kJ).

[1 mark]

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) 7.89 A

(b) 1080 kJ

Common mistakes: Forgetting to convert hours to seconds; giving answer in J not kJ

Show mark scheme and worked solution

Marking points

M1 (a) · 1 mark · Substitute values into correctly.

A1 (a) · 1 mark · Final answer for current given to 2 dp (7.89 A).

B1 (b) · 1 mark · Energy calculated as J = 1080 kJ.

Worked solution

(a) A

(b) 2 hours = 7200 s, J = 1080 kJ