# Advanced Machining Questions and Answers – EDM-Mechanism of Material Removal – 1

This set of Advanced Machining Processes Multiple Choice Questions & Answers (MCQs) focuses on “EDM-Mechanism of Material Removal – 1”.

1. What is the value of order of frequency applied between the two electrodes in EDM?
a) 1 kHz
b) 3 kHz
c) 5 kHz
d) 7 kHz

Explanation: The magnitude of frequency applied between the electrodes in EDM is about 5 kHz.

2. What are the magnitude of voltages used in Electro discharge machining?
a) 1 to 20 V
b) 20 to 120 V
c) 120 to 220 V
d) 220 to 320 V

Explanation: In EDM, the magnitude of voltages range between 20 and 120 V.

3. What are the values of gaps between the electrodes in EDM?
a) 0.001 – 0.05 mm
b) 0.01 – 0.5 mm
c) 0.1 – 5 mm
d) 1 – 15 mm

Explanation: In EDM, very small gaps that range between 0.01 – 0.5 mm are maintained.

4. How is material removed in Electro discharge machining?
a) Melt and evaporate
b) Corrode and break
c) Mechanical erosion takes place
d) None of the mentioned

Explanation: In Electro discharge machining, material is melted and then evaporated.

5. What is the radius of channel, when electrical breakdown occur?
a) 4 µm
b) 6 µm
c) 8 µm
d) 10 µm

Explanation: In EDM, the electrical breakdown occurs in dielectric in a channel of radius about 10 µm.

6. State whether the following statement is true or false regarding EDM.
“In EDM, negative ions (electrons) collide with positive ions to generate heat.”
a) True
b) False

Explanation: In Electro discharge machining, electrons collide with neutral atoms producing positive ions and further electrons.

7. What are the values of temperature that are obtained while machining using EDM?
a) 2000 to 3000ᵒC
b) 4000 to 6000ᵒC
c) 8000 to 12000ᵒC
d) 15000 to 20000ᵒC

Explanation: The temperatures obtained when the ions reach their respective electrodes, range between 8000ᵒC and 12000ᵒC.

8. What range of heat fluxes are obtained while machining using EDM?
a) 1017 W/m2
b) 1019 W/m2
c) 1024 W/m2
d) 1027 W/m2

Explanation: Heat flux up to the value of 1017 W/m2 are obtained in EDM.

9. What is the duration of sparks that are produced in Electro discharge machining?
a) 0.001 – 1 µs
b) 0.1 – 2000 µs
c) 0.2 – 100 ms
d) 100 – 2000 ms

Explanation: Duration of spark in Electro discharge machining is about 0.1 to 2000 µs.

10. State whether the following statement is true or false about material removal in EDM.
“In EDM, high pressures allow the metal to evaporate.”
a) True
b) False

Explanation: High pressures in EDM try to prevent the super-heated metal from evaporation.

11. What are the values of pressure of the plasma in EDM?
a) Up to 2 atm
b) Up to 20 atm
c) Up to 200 atm
d) Up to 2000 atm

Explanation: Pressure on the plasma channel rises to values as high as 200 atm when dielectric evaporates.

12. At the end of pulse, super-heated metal evaporates _______________
a) Explosively
b) Normally
c) Periodically
d) Occasionally

Explanation: At the end of pulse, pressure drops suddenly and super-heated metal evaporates explosively.

Sanfoundry Global Education & Learning Series – Advanced Machining.

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