Question

When coal is burned to generate electricity, 70% of the primary energy in the coal is transformed into unused heat. This means that the energy conversion efficiency from chemical to electrical energy is _____

Answer 1

0.3

Step-by-step explanation:

The energy conversion efficiency is defined as the ratio of the useful output energy being generated by an energy machine to the input energy.It is denote by η.

The input and the useful output can be electric power, chemical, mechanical power, heat, etc.

Coal is being burnt to generate energy. Let the the input energy of coal be x units.

The energy lost in unused heat = 70% of x = 0.7x units

Useful output energy = 100% - 70% = 30% of x = 0.3x units

Thus,

η = Useful Energy/ Input energy

η = 0.3x/x = 0.3

Thus,

The energy conversion efficiency from chemical to electrical energy is 0.3.