What’s the equation that links with total input, efficiency, energy and useful output energy transfer

Efficiency. The ratio of energy which was transferred to a useful form compared to the total energy initially supplied is called the efficiency of the device. Efficiencies can be written as decimals like 0.33 or percentages 33%. To convert a efficiency expressed as a decimal to a percentage you need to multiply by 100.

i need the answer to this too but idk it ; -;

small = small current large mag large current