# Thermal efficiency - MCQs with answers

## Thermal efficiency - MCQs with answers

Q1. The thermal efficiency of a steam plant is defined as?

a. The ratio of heat equivalent of electrical output to the heat of combustion of coal.

b. The ratio of heat of combustion of coal to the heat equivalent of electrical output.

c. The ratio of heat equivalent of mechanical energy transmitted to the turbine shaft to the
heat of combustion of coal.

d. The ratio of heat of combustion of coal to the heat equivalent of mechanical energy transmitted to the turbine shaft.

ANSWER: c. The ratio of heat equivalent of mechanical energy transmitted to the turbine shaft to the heat of combustion of coal.

Q2. What is the overall efficiency of the thermal plant?

a. The ratio of heat equivalent of electrical output to the heat of combustion of coal.

b. The ratio of heat of combustion of coal to the heat equivalent of electrical output.

c. The ratio of heat equivalent of mechanical energy transmitted to the turbine shaft to the
heat of combustion of coal.

d. The ratio of heat of combustion of coal to the heat equivalent of mechanical energy transmitted to the turbine shaft.

ANSWER: a. The ratio of heat equivalent of electrical output to the heat of combustion of coal.

Q3. A 100 MW steam station uses coal of calorific value of 5780 kcal/kg. The thermal efficiency is about 30% and the electrical efficiency is 93%. What would be the coal consumption per hour, when the station is delivering its full rated output?

a. 48672 kg
b. 53330 kg
c. 71876 kg
d. 31826 kg