Electricity

4 marks · Easy

An electric heater has a current of 3 A flowing when it is connected to a 230 V supply. It is left on for 10 seconds.

(a)

State the units for current, voltage and charge.

[1 mark]

(b)

Calculate the power of the heater.

[1 mark]

(c)

Calculate the total charge that flows through the heater in 10 seconds.

[1 mark]

(d)

How much energy is transferred by the heater in this time?

[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) Current: ampere (A); Voltage: volt (V); Charge: coulomb (C)

(b) 690 W

(d) 6,900 J

Show mark scheme and worked solution

Marking points

B1 (a) · 1 mark · States correct SI units: ampere for current, volt for voltage, coulomb for charge.

M1 (b) · 0.5 marks · Uses P = I × V in calculation.

A1 (b) · 0.5 marks · Power calculated as 690 W. (follow-through)

M1 (c) · 0.5 marks · Uses Q = I × t for charge.

A1 (c) · 0.5 marks · Charge calculated as 30 C. (follow-through)

M1 (d) · 0.5 marks · Uses E = I × V × t or E = P × t.

A1 (d) · 0.5 marks · Energy transferred given as 6,900 J. (follow-through)

Worked solution

a) SI units:

- Current: ampere (A)

- Voltage: volt (V)

- Charge: coulomb (C)

b) Power, P = I × V = 3 A × 230 V = 690 W

c) Charge, Q = I × t = 3 A × 10 s = 30 C

d) Energy, E = I × V × t = 3 × 230 × 10 = 6,900 J