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
Ans: a

In a domestic cake baking oven the temperature is controlled by

(a)     voltage variation
(b)     thermostat
(c) auto-transformer
(d) series-parallel operation
Ans: d

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

(a)     arc heating
(b)     resistance heating
(c) induction heating
(d) dielectric heating
Ans: b

Induction furnaces are employed for which of the following ?

(a)     Heat treatment of castings
(b)     Heating of insulators
(c) Melting aluminium
(d) None of the above
Ans: a

By the use of which of the following, high frequency power supply for induction furnaces can be obtained ?

(a)     Coreless transformers
(b)     Current transformers
(c) Motor-generator set
(d) Multi-phase transformer
Ans: c

In induction heating ______ is abnormally high.

(a)     phase angle    
(b)     frequency
(c) current
(d)     voltage
Ans: b

By which of the following methods the temperature inside arc nace can be varied ?

(a) By disconnecting some of the heating elements
(b) By varying the operating voltage
(c) By varying the current through heating elements
(d) By any of the above method
Ans: d

In a resistance furnace the atmosphere is

(a)     oxidising
(b)     deoxidising
(c)     reducing
(d)     neutral
Ans: a

The material of the heating element for a furnace should have

(a)     lower melting point
(b)     higher temperature coefficient
(c)     high specific resistance
(d)     all of the above
Ans: c

Which of the following will happen if the thickness of refractory wall of furnace is increased ?

(a)     Heat loss through furnace wall will increase
(b)     Temperature inside the furnace will fall
(c) Temperature on the outer surface of furnace walls will drop
(d) Energy consumption will increase
Ans: c

The temperature inside a furnace is usually measured by which of the following ?

(a) Optical pyrometer
(b) Mercury thermometer
(c) Alcohol thermometer
(d) Any of the above
Ans: a

A non-dimensional number generally associated with natural convection heat transfer is

(a)     Prandtl number
(b)     Grashoff number
(c)     Pecelet number
(d)     Nusselt number
Ans: b

Which of the following insulating materials was suitable for low temperature applications ?

(a)     Asbestos paper
(b)     Diatomaceous earth
(c)     80 percent magnesia
(d)     Cork
Ans: b

Induction heating process is based on which of the following principles ?

(a)     Thermal ion release principle
(b)     Nucleate heating principle
(c) Resistance heating principle
(d) Electro-magnetic induction principle
Ans: d

Which of the following has the highest value of thermal conductivity ?

(a)     Water
(b)     Steam
(c)     Solid ice
(d)     Melting ice
Ans: c

The process of heat transfer during the re entry of satellites and missiles, at very high speeds, into earth's atmosphere is known as

(a)     ablation
(b)     radiation
(c) viscous dissipation
(d) irradiation
Ans: a

Heat is transferred simultaneously by condition, convection and radiation

(a)     inside boiler furnaces
(b)     during melting of ice
(c) through the surface of the insulted pipe carrying steam
(d) from refrigerator coils to freezer of a refrigerator
Ans: a

A perfect black body is one that

(a)     transmits all incident radiations
(b)     absorbs all incident radiations
(c) reflects all incident radiations
(d) absorbs, reflects and transmits all incident radiations
Ans: b

Heat transfer by condition will not occur when

(a)     bodies are kept in vacuum
(b)     bodies are immersed in water
(c) bodies are exposed to thermal radiations
(d) temperatures of the two bodies are identical
Ans: d

For the transmission of heat from one body to another

(a)     temperature of the two bodies must be different
(b)     both bodies must be solids
(c)     both bodies must be in contact
(d)     at least one of the bodies must have some source of heating
Ans: a