Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) on “Induction Furnace – High Frequency”.
1. The oil of which metal is used in high frequency induction furnace?
a) Zinc
b) Copper
c) Aluminium
d) Iron
Answer: b
Clarification: In a high frequency induction furnace, the refractory is placed inside the water cooled copper oil and is packed into its position by ramming it.
2. A high frequency induction furnace can melt metal up to what mass?
a) 10 tons
b) 11 tons
c) 12 tons
d) 13 tons
Answer: c
Clarification: A high frequency induction furnace is used for the melting of comparatively small quantities. Metals up to the mass of 12 tons can be melted using this process.
3. What causes uniformity in the melt composition?
a) Electric stirring
b) Electric shaking
c) Magnetic stirring
d) Magnetic shaking
Answer: c
Clarification: For ensuring uniformity, a magnetic stirrer is employed, in a high frequency induction furnace. This magnetic stirrer distributes the composition of the melt excellently as needed.
4. Which currents are used for inducing heat in the high frequency induction furnace?
a) Alternating primary currents
b) Direct primary currents
c) Alternating secondary currents
d) Direct secondary currents
Answer: c
Clarification: A heavy amount of alternating secondary current, by electromagnetic induction, is induced in the metal charge. This causes the metal to get heated, because of the resistance offered by the metal charge.
5. How much is the thermal efficiency of a coreless high frequency induction furnace?
a) 50%
b) 60%
c) 70%
d) 80%
Answer: b
Clarification: As compared to a core type furnace, a coreless high frequency induction furnace has a lower efficiency. The thermal efficiency of a coreless furnace can be only up to 60%.
6. What is the minimum frequency accepted for the motor, used in current production of high frequency induction furnace?
a) 430 cycles/second
b) 500 cycles/second
c) 550 cycles/second
d) 600 cycles/second
Answer: b
Clarification: In high frequency induction furnace, motors which are equipped for the production of high frequency current can have a minimum frequency of 500 cycles every second.
7. In high frequency induction furnace, time taken by charge to melt is long.
a) True
b) False
Answer: b
Clarification: The process of melting is done very quickly by conduction and radiation, and magnetic stirring makes uniform distribution of the melt composition, which reduces time. Hence time taken by the charge to melt is short.
8. What is the minimum frequency accepted for the spark gap converter, used in current production of high frequency induction furnace?
a) 10,000 cycles/second
b) 15,000 cycles/second
c) 20,000 cycles/second
d) 25,000 cycles/second
Answer: c
Clarification: Spark gap converters which are equipped for the production of high frequency current can have a minimum frequency of 20,000 cycles every second, in high frequency induction furnace.
9. What is the maximum frequency accepted for the motor, used in current production of high frequency induction furnace?
a) 5000 cycles/second
b) 10000 cycles/second
c) 7500 cycles/second
d) 12500 cycles/second
Answer: b
Clarification: Motors which are equipped for the production of high frequency current can have a maximum frequency of 10000 cycles every second, in high frequency induction furnace.
10. What is the maximum frequency accepted for the spark gap converter, used in current production of high frequency induction furnace?
a) 70,000 cycles/second
b) 75,000 cycles/second
c) 80,000 cycles/second
d) 85,000 cycles/second
Answer: c
Clarification: None.