We know that the law of conservation of energy states that energy can not be created or destroyed. it only changes form. consider this energy transformation diagram. assume that the energy input in this case is chemical potential energy and the useful energy output is kinetic energy, specifically a small fan to keep you cool. the diagram also shows how to calculate the efficiency of the fan. if the law of conservation of energy holds true, explain why the efficiency of the fan is not 100%.
a) no machine is ever 100% efficient; some energy is not transformed.
b) some of the chemical potential energy is destroyed during the energy transformation.
c) some of the chemical potential energy is transformed into heat energy as well as kinetic energy.
d) conservation of energy also implies that some of the chemical potential energy is conserved or not used to run the fan.

The answer is C) Some of the chemical potential energy is transformed into heat energy as well as kinetic energy.

Explanation:

C) Some of the chemical potential energy is transformed into heat energy as well as kinetic energy.

Explanation:

We have to understand here the Law of conservation of energy. It states that

"Energy can neither be created nor destroyed, however, it converts from on form into other form."

Now we have to understand the difference between efficiency and conservation. If the output of a machine is not 100%, it does not imply that energy is destroyed. During the transformation process, there is always some energy, which is transformed in undesired and unavoidable way. For example, when you walk, you convert your kinetic energy into work, but you do not get 100% output, because the friction between your feet and floor convert some of your energy into heat in an undesirable way. Similarly, when chemical energy is used to run a fan, it will first convert into heat energy, now, there is no system which is 100% isolated, means you can not use all of the heat produced during burning process, but some of the heat will be lost in surrounding. Now this remaining heat will be used to produce mechanical energy which will run generator which will produce electric energy. Now during the rotation of conductor coil between the poles of a magnet, the friction also produces heat which again lost into surrounding and the remaining energy produces electric current which is again used by the motor in the fan to convert electrical energy into kinetic energy. Here the force of friction again works when rotor of motor rotates, which also produce heat and it lost again into surrounding.

So, in the process one can see that there are major frictional losses, due to which output is reduced, but the total amount of energy remains same.