Question 21
Question 21 of 40
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No letter options?
Older MCQs might not have the typical A, B, C, D choices. They have choices 1, 2, 3, and a combination of them is the answer. Below is the key that maps such combinations to the answer.
A 1, 2 and 3 are correct
B 1 and 2 only are correct
C 2 and 3 only are correct
D 1 only is correct
Topics Tested
4. Electricity and magnet...
4.4.1. Uses of electricity

Recall and use the equation energy = current × voltage × time, E = IVt

1. Motion, forces and ene...
1.7.4. Efficiency

Define efficiency as: (a) (%) efficiency = (useful energy output) / (total energy input) × 100% (b) (%) efficiency = (useful power output) / (total power input) × 100% and recall and use these equations