This set of Basic Electrical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Capacitance of a Multi Plate Capacitor”.
1. Which is the correct expression for capacitance of a multi plate capacitor?
a) C=absolute permittivity*A/d
b) C=Actual permittivity*(n-1)*A/d
c) C=Actual permittivity*(n)*A/d
d) Actual permittivity*(n+1)*A/d
View Answer
Explanation: The correct expression is: C=Actual permittivity*(n-1)*A/d.
Where, n=number of plates, A=area of cross section of the plates, d=distance of separation between the plates.
2. What happens to the capacitance of a multi plate capacitor when the area of cross section of the plate decreases?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
View Answer
Explanation: When the area of cross section decreases, the capacitance also decreases since it is related by the formula C=Actual permittivity*(n-1)*A/d. Here, we can see that the capacitance is directly proportional to the area of cross section.
3. What happens to the capacitance of a multi plate capacitor when the distance of separation between the plate increases?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
View Answer
Explanation: When the distance of separation between the plates increases, the capacitance decreases since it is related by the formula C=Actual permittivity*(n-1)*A/d. Here, we can see that the capacitance is inversely proportional to the distance of separation.
4. What happens to the capacitance of a multi plate capacitor when the number of plates increases?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
View Answer
Explanation: When the number of capacitors increases, the capacitance also increases since it is related by the formula C=Actual permittivity*(n-1)*A/d. Here, we can see that the capacitance is directly proportional to the number of capacitors.
5. Find the capacitance of a multi plate capacitor whose actual permittivity= 5F/m, n=3, A=4m2and d=2m.
a) 10F
b) 20F
c) 30F
d) 40F
View Answer
Explanation: The formula for capacitance of a multi plate capacitor: C=Actual permittivity*(n-1)*A/d.
Thus, C=5*(3-1)*4/2 = 20F.
6. Find the capacitance of a multi plate capacitor whose relative permittivity=5, n=3, A=4m2 and d=2m.
a) 1.77*10-10 F
b) 1.77*1010 F
c) 1.77*10-11 F
d) 1.77*1011 F
View Answer
Explanation: The formula for capacitance of a multi plate capacitor: C=Relative permittivity*absolute permittivity*(n-1)*A/d.
C = 5*8.85*10-12*(3-1)*4/2=1.77*10-10.
7. Find the number of plates in the multi plate capacitor having C=20F absolute permittivity=5F/m, A=4m2 and d=2m.
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: The formula for capacitance of a multi plate capacitor: C=Actual permittivity*(n-1)*A/d.
Substituting the given values in the equation, we get n=3.
8. Calculate the distance between the plates of the capacitor having C=20F, actual permittivity = 5F/m n=3 and A=4m2.
a) 1m
b) 2m
c) 3m
d) 4m
View Answer
Explanation: The formula for capacitance of a multi plate capacitor: C=Actual permittivity*(n-1)*A/d.
Substituting the given values in the equation, we get d=2m.
9. Calculate the area of cross section of the multi plate capacitor having C=20F, actual permittivity=5F/m n=3 and d=2m.
a) 1m2
b) 2m2
c) 3m2
d) 4m2
View Answer
Explanation: The formula for capacitance of a multi plate capacitor: C=Actual permittivity*(n-1)*A/d.
Substituting the given values in the equation, we get A=4m2.
10. Calculate the number of plates in the multi plate capacitor having C=1.77*10-10F relative permittivity=5, A=4m2 and d=2m.
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: The formula for capacitance of a multi plate capacitor: C=Relative permittivity*absolute permittivity*(n-1)*A/d.
Substituting the given values in the equation, we get n=3.
Sanfoundry Global Education & Learning Series – Basic Electrical Engineering.
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