All Free Electrical Engineering MCQs with Answers

• A. steel
• B. cast iron
• C. copper
• D. aluminium

Explanation: Steel withstands the high temperature and pressure of steam and has better mechanical strength than cast iron or aluminium.

• A. steam in pipes surrounded by water
• B. water in pipes surrounded by steam
• C. either A. or (b)
• D. none of the above

Explanation: In an evaporative condenser, steam flows inside tubes while water is sprayed over their outer surfaces and evaporates to remove heat.

• A. there is one pump to remove air and condensate
• B. there are two pumps to remove air and condensate
• C. there are three pumps to remove air, vapour and condensate
• D. there is no pump, the condensate gets removed by gravity

Explanation: A regenerative surface condenser uses separate pumps because air and condensate have different functions and are withdrawn separately.

• A. to maintain pressure below atmospheric to increase work output from the primemover
• B. to receive large volumes of steam exhausted from steam prime mover
• C. to condense large volumes of steam to water which may be used again in boiler
• D. all of the above

Explanation: A condenser receives turbine exhaust steam, maintains a vacuum to increase turbine work, and converts the steam back into reusable…

• A. removes air and also vapour from condenser
• B. removes only air from condenser
• C. removes only un-condensed vapour from condenser
• D. removes air alongwith vapour and also the condensed water from condenser

Explanation: An Edward's air pump is a wet air pump that removes air together with uncondensed vapour and condensate from the condenser.

• A. increases the quantity of vapour extracted along with air
• B. reduces the quantity of vapour extracted along with air
• C. does not affect vapour quantity extracted but reduces pump capacity of air extraction pump
• D. none of the above

Explanation: The cooling section condenses much of the vapour mixed with the extracted air before it reaches the air pump.

• A. fall in absolute pressure maintained in condenser
• B. rise in absolute pressure maintained in condenser
• C. no change in absolute pressure in the condenser
• D. rise in temperature of condensed steam

Explanation: Air entering a condenser raises its partial pressure and opposes condensation; removing it lowers the total absolute pressure and improves…

• A. steam and cooling water mix to give the condensate
• B. cooling water passes through the tubes and steam surrounds them
• C. steam passes through the cooling tubes and cooling water surrounds them
• D. all of the above varying with situation

Explanation: A shell-and-tube surface condenser keeps the fluids separate: cooling water flows inside the tubes and exhaust steam surrounds the tubes…

• A. cooling water passes through tubes and steam surrounds them
• B. steam passes through tubes and cooling water surrounds them
• C. steam and cooling water mix
• D. steam and cooling water do not mix

Explanation: Jet condensers are direct-contact condensers, so cooling water comes into direct contact and mixes with the exhaust steam.

• A. higher
• B. lower
• C. same as long as initial pressure and temperature is unchanged
• D. none of the above

Explanation: A condenser reduces the exhaust pressure and permits greater expansion of the steam, increasing the turbine work and thermal efficiency.

• A. increases with the increase in number of stages
• B. decreases with the increase in number of stages
• C. remains same irrespective of number of stages
• D. none of the above

Explanation: The reheat factor is the ratio of the sum of stagewise actual enthalpy drops to the overall isentropic enthalpy drop.

• A. Throttle governing
• B. Nozzle control governing
• C. By-pass governing
• D. all of the above

Explanation: Steam turbines may be controlled by throttling the inlet steam, regulating flow through selected nozzles, or admitting steam through a…

• A. 0.5 to 0.6
• B. 0.9 to 0.95
• C. 1.02 to 1.06
• D. 1.2 to 1.6

Explanation: Because stagewise expansion losses accumulate, the reheat factor is slightly greater than unity, normally about 1.02 to 1.06.

• A. 75%
• B. 100%
• C. 50%
• D. 60%

Explanation: In a Parsons turbine, the enthalpy drop is divided equally between the fixed and moving blades.

• A. pressure compounded steam turbine
• B. simple single wheel, impulse steam turbine
• C. simple single wheel reaction steam turbine
• D. multi wheel reaction steam turbine

Explanation: A Parsons turbine is a multistage reaction turbine, commonly described as a multi-wheel reaction turbine.

• A. reaction steam turbine
• B. velocity compounded impulse steam turbine
• C. pressure compounded impulse steam turbine
• D. pressure velocity compounded steam turbine

Explanation: The Rateau arrangement divides the total pressure drop among several stages, with each stage operating on the impulse principle.

• A. there is enthalpy drop both in fixed and moving blades
• B. there is enthalpy drop only in fixed blades
• C. there is enthalpy drop only in moving blades
• D. none of the above

Explanation: A reaction turbine has pressure and enthalpy drops in both the stationary and moving blade passages.

• A. near bottom of chimney
• B. near bottom of furnace
• C. at the top of the chimney
• D. anywhere permissible

Explanation: In an induced-draught system, the fan is placed in the hot-gas path between the boiler and chimney, commonly near the bottom of the…

• A. less smoke
• B. more draught
• C. less chimney gas temperature
• D. all of the above

Explanation: Artificial draught improves combustion, reduces smoke, and allows the gases to leave with a lower temperature than in poorly controlled…

• A. air fans
• B. steam jet
• C. fan or steam jet
• D. all of the above

Explanation: Artificial draught is created mechanically by fans or pneumatically by steam jets. Therefore, both a fan and a steam jet can produce it.