iGCSE Physics (0625) 1.7.1 Energy Paper 4 -Exam Style Questions- New Syllabus
Question
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic $1.7.1$ — Energy (Part $\mathrm{(a)(i)}$)
• Topic $1.7.3$ — Energy resources (Parts $\mathrm{(a)(ii)}$, $\mathrm{(b)}$)
▶️ Answer/Explanation
(a)(i)
For the correct answer:
$1135\text{ MW}$ (which is $\approx 1100\text{ MW}$)
According to the principle of conservation of energy, the total power input must equal the sum of the useful power output and all wasted power. From Fig. 3.1, the total wasted power is $2200\text{ MW} + 40\text{ MW} + 25\text{ MW} = 2265\text{ MW}$. Subtracting this from the total input of $3400\text{ MW}$ gives $\text{useful output} = 3400 – 2265 = 1135\text{ MW}$.
(a)(ii)
For the correct answer:
$33\%$ (or $0.33$)
Efficiency is calculated using the formula $\text{Efficiency} = \frac{\text{useful power output}}{\text{total power input}} \times 100\%$. Using the values from the previous step, $\text{Efficiency} = \frac{1135}{3400} \times 100 = 33.38\%$, which rounds to $33\%$.
(b)
For the correct answer:
Water is heated by hot rocks underground to produce steam, which turns a turbine.
Geothermal energy involves pumping cold water down into the Earth’s crust where it comes into contact with hot rocks. The thermal energy transfers to the water, turning it into steam. This steam drives a turbine connected to an electrical generator.