O-LevelPhysicsEnergy & Work5054/22 · May/June 2021 · Q915 Marks

9 (a) Fig. 9.1 represents the conversion of energy in a mobile phone. [Figure 9.1]

(a)(i)State the form of energy stored in the battery.[1]
(a)(ii)State the useful form of output energy from the battery.[1]
(a)(iii)State two useful forms of output energy from the mobile phone.[2]
(b)When the battery is in use, the average current is 1.3mA. Determine the charge that passes through the battery in a time of 2.0 minutes. charge =[2]
(c)(i)Calculate the thermal energy (heat) needed to raise the temperature of the battery by 5.0°C. thermal energy =[3]
(c)(ii)State what is meant by efficiency.[2]
(c)(iii)Calculate the efficiency of the battery. efficiency =[2]
(c)(iv)Suggest and explain one reason why the value for the efficiency calculated in (iii) is larger than the actual efficiency of the battery.[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.

[B1] chemical
[B1] electrical
[B2] ANY 2 from • light • sound • radio / microwave / electromagnetic (waves)
[C1] (Q =) It in any form
[A1] 0.16 C
[C1] (E =) mcT numerical or algebraic in any form
[C1] 0.11 × 830 × 5
[A1] 460 J
[C1] energy output / energy input or useful energy output / (total) energy input
[C1] (energy input =) 460 + 5200 or 5660 (J) seen or 5200 ÷ (energy in 9(c)(i) + 5200)
[A1] 92% or 0.92
[B1] (thermal) energy lost / heat lost (from battery to environment)
[B1] energy input larger than calculated / 5660 (J) or temperature rise should be larger / is smaller than it should be or thermal energy / heat produced larger than 460 J / calculated

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