A. Variation of resistance
B. Variation of voltage
C. Periodical switching on and off of the supply
D. All of the above methods
Related Mcqs:
- 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
E. all of the above ways - For intermittent work which of the following furnaces is suitable ?
A. Indirect arc furnace
B. Core less furnace
C. Either of the above
D. None of the above - 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 - 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 - Direct arc furnaces have which of the following power factors ?
A. Unity
B. Low, lagging
C. Low, leading
D. Any of the above - It is desirable to operate the arc furnaces at power factor of_____________?
A. zero
B. 0.707 lagging
C. unity
D. 0.707 leading - 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 - In resistance heating highest working temperature is obtained from heating elements made of_____________?
A. nickel copper
B. nichrome
C. silicon carbide
D. silver - Which of the following methods of heating is not dependent on the frequency of supply ?
A. Induction heating
B. Dielectric heating
C. Electric resistance heating
D. All of the above - Which of the following heating methods has maximum power factor ?
A. Arc heating
B. Dielectric heating
C. Induction heating
D. Resistance heating
