Physics for IGCSE & O level - Forces And Energy (Section 9 - No. 12)

What is the formula for efficiency?

Efficiency = (total energy input) / (useful energy output) x 100%

Efficiency = (useful energy output) / (total energy input) x 100%

Efficiency = work done / time taken x 100%

Efficiency = power output / time taken x 100%

Efficiency = (useful energy output) / (total energy input) x 100%