Question

Electrical energy is used to turn the blades of a fan. The amount of energy transformed is seen here : 750 J electrical energy is transformed into 400 J kinectic energy . What happened to the remaining 350j of energy?

Answer 1

Electrical energy is used to run the fan

Here as per given condition 750 J of electrical energy is used to run the fan which is converted into Kinetic energy as 400 J

So here we can see that 350 J of energy is lost against many other type of frictional and resistive loses.

So here we can say that out of 750 J of energy only 400 J is used to run the fan and rest amount of energy is lost against friction.

also we can say that efficiency of this fan will be

$\eta = \frac{Useful}{Total}$

$\eta = \frac{400}{750}$

$\eta = \frac{8}{25}$