Explore topic-wise MCQs in Design Electrical Machines.

This section includes 21 Mcqs, each offering curated multiple-choice questions to sharpen your Design Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.

1.

What is the formula for the temperature rise of the transformers?

A. temperature rise = total loss * specific heat dissipation * surface temperature
B. temperature rise = total loss / (specific heat dissipation * surface temperature)
C. temperature rise = total loss / specific heat dissipation / surface temperature
D. temperature rise = total loss * specific heat dissipation / surface temperature
E. temperature rise = total loss / specific heat dissipation / surface temperatured) temperature rise = total loss * specific heat dissipation / surface temperature
Answer» C. temperature rise = total loss / specific heat dissipation / surface temperature
Discussion
2.

What is the specific heat dissipated by the plain walled tanks of the transformer by radiation and convection?

A. 6.5, 6 W per m2 – °C
B. 6, 6.5 W per m2 – °C
C. 6.5, 6.5 W per m2 – °C
D. 6, 6 W per m2 – °C
Answer» C. 6.5, 6.5 W per m2 – °C
Discussion
3.

How do the walls of the transformer tank dissipate heat?

A. by radiation
B. by convection
C. by conduction
D. by convection and radiation
Answer» E.
Discussion
4.

The convection due to air is 10 times the convection due to oil.

A. true
B. false
Answer» C.
Discussion
5.

What is the value of specific heat dissipation for convection due to air?

A. 8 W per m2 – °C
B. 6 W per m2 – °C
C. 9 W per m2 – °C
D. 10 W per m2 – °C
Answer» B. 6 W per m2 – °C
Discussion
6.

The problem of temperature rise and cooling of transformers is essentially the same as that of rotating machinery.

A. true
B. false
Answer» B. false
Discussion
7.

WHAT_IS_THE_VALUE_OF_SPECIFIC_HEAT_DISSIPATION_FOR_CONVECTION_DUE_TO_AIR??$

A. 8 W per m2- 0C
B. 6 W per m2- 0C
C. 9 W per m2- 0C
D. 10 W per m2- 0C
Answer» B. 6 W per m2- 0C
Discussion
8.

How do the walls of the transformer tank dissipate heat?$

A. by radiation
B. by convection
C. by conduction
D. by convection and radiation
Answer» E.
Discussion
9.

The_convection_due_to_air_is_10_times_the_convection_due_to_oil?$

A. true
B. false
Answer» C.
Discussion
10.

How are the ratings of the transformer, losses and temperature rise related?

A. increase, decrease, increase
B. decrease, increase, increase
C. increase, increase, increase
D. decrease, increase, decrease
Answer» D. decrease, increase, decrease
Discussion
11.

Can the plain walled tanks accommodate the transformer for both large and small outputs?

A. the plain walled tanks can accommodate for large outputs but cannot accommodate for small outputs
B. the plain walled tanks can accommodate for large outputs and small outputs
C. the plain walled tanks cannot accommodate for large outputs and small outputs
D. the plain walled tanks can accommodate for small outputs but cannot accommodate for large outputs
Answer» E.
Discussion
12.

What is the formula for temperature rise of the transformers?

A. temperature rise = total loss * specific heat dissipation * surface temperature
B. temperature rise = total loss / (specific heat dissipation * surface temperature)
C. temperature rise = total loss / specific heat dissipation / surface temperature
D. temperature rise = total loss * specific heat dissipation / surface temperature
Answer» C. temperature rise = total loss / specific heat dissipation / surface temperature
Discussion
13.

What_is_the_specific_heat_dissipated_by_the_plain_walled_tanks_of_the_transformer_by_radiation_and_convection?

A. 6.5, 6 W per m2- 0C
B. 6, 6.5 W per m2- 0C
C. 6.5, 6.5 W per m2- 0C
D. 6, 6 W per m2- 0C
Answer» C. 6.5, 6.5 W per m2- 0C
Discussion
14.

What is the formula for specific heat dissipation due to convection of oil?

A. specific heat dissipation = 40.3*(temperature difference of the surface relative to oil / height of the dissipating surface)1/4 W per m2- 0C
B. specific heat dissipation = 40.3 / (temperature difference of the surface relative to oil / height of the dissipating surface)1/4 W per m2- 0C
C. specific heat dissipation = 40.3*(temperature difference of the surface relative to oil * height of the dissipating surface)1/4 W per m2- 0C
D. specific heat dissipation = 40.3*(temperature difference of the surface relative to oil + height of the dissipating surface)1/4 W per m2- 0C
Answer» B. specific heat dissipation = 40.3 / (temperature difference of the surface relative to oil / height of the dissipating surface)1/4 W per m2- 0C
Discussion
15.

What is the range of the working temperature of oil determined by the tests?

A. 40-600 C
B. 30-600 C
C. 45-600 C
D. 50-600 C
Answer» E.
Discussion
16.

What type of heat dissipation takes place when heat flows from the walls of the cooler to the cooling medium?

A. convection
B. radiation
C. convection and radiation
D. conduction and radiation
Answer» D. conduction and radiation
Discussion
17.

What type of heat dissipation takes place when heat flows from oil to walls of a cooler?

A. conduction
B. convection
C. radiation
D. conduction and convection
Answer» C. radiation
Discussion
18.

What type of heat dissipation takes place when the heat flows from the outer surface of the transformer part to the oil that cools it?

A. conduction
B. convection
C. conduction and convection
D. radiation
Answer» C. conduction and convection
Discussion
19.

In how many ways does heat dissipation occur in transformers?

A. 2
B. 3
C. 4
D. 5
Answer» C. 4
Discussion
20.

How are the losses in the transformer and rotating machines converted to?

A. the losses are converted to electrical energy
B. the losses are converted to electrical and mechanical energy
C. the losses are converted to mechanical energy
D. the losses are converted to thermal energy
Answer» E.
Discussion
21.

The problem of temperature rise and cooling of transformers is essentially the same as that of rotating machinery?

A. true
B. false
Answer» B. false
Discussion