IB Physics HL A.3.13 Efficiency Question Bank

Practise HL efficiency calculations for turbines, solar panels, transformers, motors and multi-stage power systems and design questions.

[Maximum number: 5]

This question is about energy sources.

A small island is situated in the Arctic. The islanders require an electricity supply but have no fossil fuels on the island. It is suggested that wind generators should be used in combination with power stations using either oil or nuclear fuel.

(a)

Conventional horizontal-axis wind generators have blades of length 4.7 m .

The average wind speed on the island is $7.0 \mathrm{~ms}^{-1}$ and the average air density is $1.29 \mathrm{~kg} \mathrm{~m}^{-3}$ .

[ 2 ]

(i)

Explain why less energy can actually be generated by the wind generators than the value you deduced in (b)(i).

[ 2 ]

(b)

The energy flow diagram (Sankey diagram) below is for an oil-fired power station that the islanders might use.

[ 3 ]

(i)

Determine the efficiency of the power station.

[ 2 ]

indication that energy supplied to islanders is output and chemical energy input / $\frac{8}{25}$ used;
32 \% / 0.32;

(ii)

Explain why energy is wasted in the power station.

[ 1 ]

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A.3.13—Efficiency question 1

Question (a)

Question (i)

Question (b)

Question (i)

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