O-LevelPhysicsThermal Physics5054/21 · May/June 2019 · Q25 Marks

Some sources of energy, used to produce electricity, may run out in the future. Underline the two sources of energy that are likely to run out first, before the others. coal oil solar tides wave wind

(a)Some sources of energy, used to produce electricity, may run out in the future. Underline the two sources of energy that are likely to run out first, before the others. coal oil solar tides wave wind[1]
(b)(i)Thermal energy is given to the water as it passes through rocks underground. Describe the process by which this thermal energy causes the turbine to turn.[2]
(b)(ii)Water from the cooling tower at 30°C passes into the ground and is heated to 160°C. The specific heat capacity of water is 4200 J/(kg°C). Calculate the thermal energy (heat) needed to heat 90 kg of water from 30°C to 160°C.[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

[1] coal and oil underlined
[1] water boils or turns to steam
[1] pressure / force of steam turns turbine or steam at high pressure / pressure difference (across turbine)
[1] (Q =) mcT numerical or algebraic
[1] 4.9 × 10^7 J

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