Capacitors and dielectrics

Question 1

Define capacitance.

Answer 1

Capacitance of the conductor is the ratio of charge to the potential through which the charge rises.

Question 2

Give the formula of capacitance.

Answer 2

C=Q/V

Question 3

What is the unit of capacitance?

Answer 3

Farad

Question 4

State the factors affecting capacitance.

Answer 4

1) Size of the conductor
2) Nature of the medium
3) neighborhood of other conductors

Question 5

Why does a practical capacitor has 2 conductor?

Answer 5

As by taking 2 conductors the capacitance or the capacity to hold the charges increases.

Question 6

What is the capacitance of a parallel plate capacitor?

Answer 6

C=K(E0A/d)

Question 7

Give the formula for capacitors in series and parallel.

Answer 7

Series-1/Cs=1/C1 + 1/C2 +…..1/Cn

Parallel- Cp=C1 + C2 +…..Cn

Question 8

Give differences between capacitors in series and parallel.

Answer 8

1)Series-Charge is constant
Parallel-Potential is constant
2)Series-Potential varies across the capacitors
Parallel-Charge varies across the conductors

Question 9

What is the energy stored in charged capacitor? (3 formulaes)

Answer 9

U=½Q^2/C
U=½QV
U=½CV^2

Question 10

Give the principle of the capacitance.

Answer 10

The principle of the capacitance states that if an uncharged conductor is placed near the charged conductor than it’s capacitance rises.

Question 11

Give formula of energy density of an electric field.

Answer 11

Ue=½ε0 E^2

Question 12

What is energy density?

Answer 12

Energy stored per unit volume in a body

Question 13

What is the potential when charges are shared?

Answer 13

V=C1V1+C2V2/c1+c2

Question 14

What is the work done when charges are shared?

Answer 14

W=½(C1V1+C2V2)^2 / C1+C2

Question 15

What is the energy loss redistribution of the charges?

Answer 15

W loss=½C1C2/C1+C2*(V1-V2)^2

Question 16

All dielectric materials are ____________.

Answer 16

Insulators

Question 17

What is the induced charge on dielectric slab?

Answer 17

q=Q(1-1/K)

Question 18

What is the capacitance of a dielectric partly filling the space?

Answer 18

C=ε0A/(d-t) + t/K

Question 19

What is the capacitance for mixed dielectric slab?

Answer 19

C=ε0A/(t1/k1 + t2/k2)

Question 20

What is the metallic slab independent of?

Answer 20

It is independent of the values of a and b, where a is the thickness of the upper portion and b is the thickness of lower portion.

Question 21

What is the filed inside dielectric?

Answer 21

E=E0/K

Question 22

What are the types of molecules inside dielectric?

Answer 22

Polar molecules

Question 23

The ______ necessary to cause the breakdown of a dielectric measures its _______.

Answer 23

Potential gradient, dielectric strength

Question 24

What is the unit of dielectric strength.

Answer 24

kV/mm

Question 25

What does breakdown of voltage depends on?(2 points)

Answer 25

nature of dielectric and geometry of capacitor