Electric Power

As number of turns are halved so length of wire is halved, and radius is doubled, then area will be 4 times the previous one if previous resistance is R then new resistance is R/8 and if previous emf is E then new emf will be E/2 so
P_i =
P_f =
As the answer key is changing students can challenge this question.

The power of a motor is given by: where is the mass of water raised, is the acceleration due to gravity, is the height, and is the time taken.

For the two motors:

Simplify the powers:

The ratio of powers is given by:

Equating this with the given ratio:

Cross-multiply:

Simplify:

Square both sides:

Expand and simplify: