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
Related Mcqs:
- 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 - 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 - Due to which of the following reasons it is desirable to have short arc length ?
A. To achieve better heating
B. To increase the life of roof refractory
C. To have better stirring action
D. To reduce problem of oxidation
E. All of the above - In direct arc furnace, which of the following has high value ?
A. Current
B. Voltage
C. Power factor
D. All of the above - Direct arc furnaces have which of the following power factors ?
A. Unity
B. Low, lagging
C. Low, leading
D. Any of the above - The electrode of a direct arc furnace is made of____________?
A. tungsten
B. graphite
C. silver
D. copper - 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 - It is desirable to operate the arc furnaces at power factor of_____________?
A. zero
B. 0.707 lagging
C. unity
D. 0.707 leading - 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
