Edexcel IGCSEPhysicsGeneral Applications11 Marks

A small electric motor is connected to a 6.0 V battery. The current in the motor is 0.40 A.

(a)Calculate the energy transferred by the battery in 5.0 minutes. Show your working.[3]
(b)(i)The motor is used to lift a 0.20 kg mass at a constant velocity through a height of 1.5 m. The gravitational field strength is 9.8 N/kg. Calculate the useful energy transferred to the mass. Show your working.[2]
(b)(ii)Calculate the efficiency of the motor. Show your working.[3]
(c)Describe how the energy transfer in the motor causes a temperature increase in the surroundings.[3]

Mark scheme

Marking points from the official mark scheme. The mark or mark type is shown in brackets.

12 (a) M1 for (time conversion) 5.0 × 60 = 300 (s)
M1 for E = V × I × t OR P = V × I
A1 for 6.0 × 0.40 × 300 = 720 (J)
12 (b)(i) M1 for GPE = mgh OR 0.20 × 9.8 × 1.5
A1 for 2.94 (J)
12 (b)(ii) M1 for efficiency = useful energy out ÷ total energy in OR 2.94 ÷ 720
M1 for conversion to percentage OR × 100
A1 for 0.0041 OR 0.41%
12 (c) M1 for (some) energy is wasted (as heat/sound)
A1 for (due to) friction / air resistance / resistance (of coils)
A1 for thermal energy / heat (from motor) transferred to surroundings

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