# Power Plant Questions and Answers – Efficiencies in a Steam Power Plant – 1

This set of Power Plant Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Efficiencies in a steam power plant – 1”.

1. What percentage of fuel energy is actually converted to electrical energy?
a) 50%
b) 40%
c) 34%
d) 25%

Explanation: In overall process due to losses the 66% of energy is lost.

2. Maximum energy of a power plant is lost in __________
a) condensor
b) pump
c) boiler
d) environment

Explanation: In a condensor heat is rejected to cooling water. This is the loss due to heat to work energy conversion in the cycle.

3. The lower is the value of heat rate __________ is the efficiency.
a) lower
b) higher
c) same
d) depends on further parameters

Explanation: The parameter that readily reflects the fuel economy is the heat rate, which is inversely proportional to the efficiency.

4. Overall efficiency is the ratio of power available at generator terminals to rate of energy released by combustion of fuel.
a) true
b) false
c) can’t say
d) not true for all conditions

Explanation: Efficiency is power generated / power supplied.

5. The steam from steam generator of a nuclear power plant is best described as __________
a) superheated steam
b) supercritical steam
c) saturated dry steam
d) saturated wet steam

Explanation: Steam contains moisture after coming out of boiler.
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6. Under certain conditions, the specific enthalpies of dry steam, saturated water and wet steam are 2783 kJ/kg, 1219 kJ/kg and 2750 kJ/kg respectively. Determine the dryness fraction of wet steam.
a) 0.01
b) 0.02
c) 0.021
d) 0.03

Explanation:Specific enthalpies of saturated water (hl) and dry steam (hs) are 1219 kJ/kg and 2783 kJ/kg. Substituting these values in the equation “hws= xdhg+(1-xd)hl” gives the dryness fraction as 0.021.

7. What includes fixed cost?
a) cost of land, Cost of building, Cost of equipment, Cost of installation
b) interest
c) management cost
d) all of the mentioned

Explanation: These are the parameters that cannot be neglected and come under the fixed cost.

8. Name the major isotope present in steam generated in a Boiling Water Reactor.
a) N-16
b) D-32
c) N-32
d) D-16

Explanation: It is more economical and more efficient.

9. Efficiency of a power plant is more in summers or winters?
a) summers
b) winters
c) same in both
d) depends on variation

Explanation: In summers the heat loss is more so efficiency is less.

10. What is the mechanical efficiency of turbine?
a) brake output / internal output
b) internal output / brake output
c) blade energy / energy supplied
d) none of the mentioned

Explanation: None.

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