Electrical Heating -- Electrical Engineering (MCQ) questions and answers

1.Which of the following is an advantage of heating by electricity?

A. Quicker operation
B. Higher efficiency
C. Absence of flue gases
D. All of these

2. The temperature inside a resistance furnace can be varied by

A.Disconnecting some of the heating elements
B. Varying the operating voltages
C. By any of the above method
D. Varying the current through heating elements

3. High frequency power supply for induction furnaces can be obtained by

A. Coreless transformers
B. Current transformers
C. Motor-generator set
D. Multi-phase transformer

4. Induction furnaces are employed for which of the following?

A. Heating of insulators
B. Heat treatment of castings
C. Melting aluminium
D. None of the above

5.In an electric room heat convector, the method of heating used is

A. Arc heating
B. Dielectric heating
C. Induction heating
D. Resistance heating

6.In a domestic cake baking oven the temperature is controlled by

A. Voltage variation
B.Thermostat
C. Auto-transformer
D. Series-parallel operation

7. In an electric press, mica is used

A. As an insulator
B. As a device for power factor improvement
C. For dielectric heating
D. For induction heating

8.Induction heating takes place in which of the following?

A. Insulating materials
B. Conducting materials which are magnetic
C. Conducting materials which are non-magnetic
D. Conducting materials which may or may not be magnetic

9.For heating element high resistivity material is chosen to

A. Reduce the length of heating element
B. Increase the life of the heating element
C. Reduce the effect of oxidation
D. Produce large amount of heat

10.In resistance heating highest working temperature is obtained from heating elements made of ____________

A. Nickel copper
B. Nichrome
C. Silicon carbide
D. Silver

11.In the indirect resistance heating method, maximum heat-transfer takes place by.

A. Convection
B. Resistance
C. Conduction
D. Radiation

12. Low temperature co-efficient of heating element is desired due to which of the following reasons?

A.To avoid initial rush of current
B. To avoid change in kW rating with temperature
C.Both (a) and (b)
D. Either (a) or (b)

13.It is desirable to operate the arc furnaces at power factor of

A. Zero
B. Unity
C.0.707 lagging
D.0.707 leading

14. Ajax Wyatt furnace is started when

A. It is filled below core level
B. It is filled above core level
C. It is fully empty
D.None of the above

15.Direct arc furnaces have which of the following power factors?

A.Low, leading
B.Unity
C. Any of the above
D.Low, lagging

16. In electric press, mica is used because it is

A.Bad conductor of heat and good conductor of electricity.
B.Bad conductor of heat and Bad conductor of electricity.
C. Good conductor of heat and Good conductor of electricity.
D. Good conductor of heat and Bad conductor of electricity.

17. Hysteresis loss and eddy current loss are used in

A. Induction heating of steel
B. Dielectric heating
C. Resistance heating
D. Induction heating of brass

18. The electrode of a direct arc furnace is made of

A. Tungsten
B.Copper
C. Silver
D.Graphite

19.Radiant heating is used for which of the following?

A. Drying of paints and varnishes
B. Heating of liquids in electric kettle
C.Melting of ferrous metals
D.Annealing of metals

20.Which devices is necessarily required for automatic temperature control in a furnace?

A.Thermostat
B. Auto-transformer
C. Thermocouple
D. Heating elements of variable resistance material