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This set of Advanced Machining Processes Quiz focuses on “ECM-Basic Working Principles”.

1. What is the approximate value of faraday’s constant?
a) 65,200 C
b) 53,800 C
c) 96,500 C
d) 85,600 C

Explanation: 1 faraday equals to approximately 96500 C.

2. In the following ratios of metal dissolved amounts, which one represent the current efficiency?
a) Observed to theoretical
b) Theoretical to observed
c) All of the mentioned
d) None of the mentioned

Explanation: In electrochemical machining, current efficiency is the ratio of observed amount of metal dissolved to the theoretical amount of metal dissolved.

3. Apparent current efficiency is due to which of the following factors?
a) Choice of wrong valence
b) Passivation of anodic surface
c) Gas evolution at anode
d) All of the mentioned

Explanation: Current efficiency may be apparent because of choice of wrong valence, passivation of anodic surface or gas evolution at anodic surface.

4. State whether the following statement is true or false regarding the working principles.
“In ECM, grain boundary attacks remove the grains through electrolytic forces.”
a) True
b) False

Explanation: In ECM, grain boundary attacks are the cause for removal of grains by electrolytic forces.

5. In ECM, gap increase proportional to which relation of time below?
a) Square of time
b) Square root of time
c) Cube of time
d) Cube root of time

Explanation: In Electrochemical machining, gap increases proportional to the square root of time.

6. At constant feed rates what happens to gap thickness?
a) Increases
b) Decreases
c) Becomes constant
d) None of the mentioned

Explanation: At constant feed rate, work piece becomes stationary and thus the gap thickness becomes constant.

7. At constant gap thickness material removal becomes equal to feed rate. What is this gap called?
a) Equal gap
b) Equilibrium gap
c) Unique gap
d) Narrow gap

Explanation: When rate of material removal per unit area is same as feed rate, then corresponding thickness is called as equilibrium thickness indicated by ‘ye’.

8. If the gap thickness is greater than equilibrium thickness what will be MRR?
a) MRR is less than feed rate
b) MRR is greater than feed rate
c) MRR is equal to feed rate
d) None of the mentioned

Explanation: When gap thickness is greater than equilibrium thickness, MRR will be less than feed rate.

9. During ECM drilling, decrease in feed rates lead to which type of machining gaps?
a) Wider
b) Narrow
c) Small
d) None of the mentioned

Explanation: Decrease in feed rate lead to wider gap thickness in ECM drilling.

10. Too small gap causes which of the following effects?
a) Sparking
b) Short circuit
c) Sparking & Short circuit
d) None of the mentioned 