It is desirable to operate the arc furnaces at power factor of_____________?

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

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

Radiations from a black body are proportional to____________?

A. T1
B. T2
C. T3
D. T*

Which of the following methods is used to control temperature in resistance furnaces ?

A. Variation of resistance
B. Variation of voltage
C. Periodical switching on and off of the supply
D. All of the above methods

In arc furnace the function of choke is______________?

A. To stabilize the arc
B. To imprpve, power factor
C. To reduce severity of the surge
D. None of the above

Hysteresis loss and eddy current loss are used in____________?

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

In electric press, mica is used because it is _________ conductor of heat but/and __________ conductor of electricity?

A. Bad, good
B. Bad, bad
C. Good, bad
D. Good, good

In heating the ferromagnetic material by induction heating, heat is produced due to_____________?

A. Induced current flow through the charge
B. Hysteresis loss taking place below curie temperature
C. Due to hysteresis loss as well as eddy current loss takingplace in the charge
D. None of the above factors

Resistance variation method of temperature control is done by connecting resistance elements in_____________?

A. series
B. parallel
C. series-parallel connections
D. star-delta connections

Which of the following devices is necessarily required for automatic temperature control in a furnace ?

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