A phone charger supplies a current of 0.80 A for 45 minutes.
(a) Calculate the charge that flows into the phone. [3]
(b) The charger has an output voltage of 5.0 V.
Calculate the energy transferred to the phone in this time. [2]
- (a) $t = 45 \times 60 = 2700$ s(1)
- (a) charge = current × time or $Q = 0.80 \times 2700$(1)
- (a) 2160 C allow 2200 C(1)
- (b) energy = charge × voltage or $E = 2160 \times 5.0$ allow ecf from (a); allow $E = I \times V \times t = 0.80 \times 5.0 \times 2700$(1)
- (b) 10 800 J allow 11 000 J or 11 kJ(1)
- Answer: (a) 2160 C (b) 10 800 J
- Examiner tip: Time must be in seconds — 0.80 × 45 = 36 C gives the wrong answer for both parts.