CIE iGCSE Co-Ordinated Science P1.6.2 Work Exam Style Questions Paper 4

(a)(i) Electrical power is generated from geothermal resources by:

• Hot water / steam is obtained from underground (from geothermal reservoirs).
• The steam is used to turn a turbine.
• The turbine turns a generator, which produces electrical power.

Geothermal energy comes from the heat stored beneath the Earth’s surface. In volcanic or geologically active areas, groundwater is heated by hot rocks deep underground. This water can be pumped up as steam or hot water. The steam drives turbines connected to generators, converting the thermal energy into kinetic energy and then into electrical energy.

(a)(ii) Two other energy resources that do not rely on radiation from the Sun:

• Nuclear (nuclear fission).
• Tidal (energy from the Moon’s gravitational pull).

Energy resources that do not rely on the Sun include:

• Nuclear energy: Energy released from nuclear fission (splitting of heavy nuclei like uranium-235) or nuclear fusion (joining of light nuclei). This energy comes from atomic nuclei, not from the Sun.
• Tidal energy: Energy from the rise and fall of ocean tides, which is caused by the gravitational pull of the Moon (and to a lesser extent, the Sun).

(b)(i) Useful power output = 450 W.

Efficiency is defined as:

\( \text{Efficiency} = \frac{\text{Useful power output}}{\text{Total power input}} \times 100\% \)

Rearranging to find the useful power output:

\( \text{Useful power output} = \text{Efficiency} \times \text{Total power input} \)

\( \text{Useful power output} = 0.32 \times 1400 = 448 \text{ W} \approx 450 \text{ W} \)

(b)(ii) Area required = 5.6 m².

The power output per square metre is 450 W/m² (from part (b)(i)). To supply a 2.5 kW (2500 W) oven:

\( \text{Area required} = \frac{2500}{450} = 5.56 \approx 5.6 \text{ m}^2 \)

(b)(iii) Gain in gravitational potential energy = 490 J.

The gain in gravitational potential energy is calculated using:

\( \Delta E_p = mg\Delta h \)

Where:
• \( m = 8.4 \text{ kg} \) (mass of the panel)
• \( g = 9.8 \text{ N/kg} \) (gravitational field strength)
• \( \Delta h = 6.0 \text{ m} \) (height lifted)

\( \Delta E_p = 8.4 \times 9.8 \times 6.0 = 493.92 \approx 490 \text{ J (to 2 significant figures)} \)