Capacitors and dielectrics Flashcards
Define capacitance.
Capacitance of the conductor is the ratio of charge to the potential through which the charge rises.
Give the formula of capacitance.
C=Q/V
What is the unit of capacitance?
Farad
State the factors affecting capacitance.
1) Size of the conductor
2) Nature of the medium
3) neighborhood of other conductors
Why does a practical capacitor has 2 conductor?
As by taking 2 conductors the capacitance or the capacity to hold the charges increases.
What is the capacitance of a parallel plate capacitor?
C=K(E0A/d)
Give the formula for capacitors in series and parallel.
Series-1/Cs=1/C1 + 1/C2 +…..1/Cn
Parallel- Cp=C1 + C2 +…..Cn
Give differences between capacitors in series and parallel.
1)Series-Charge is constant
Parallel-Potential is constant
2)Series-Potential varies across the capacitors
Parallel-Charge varies across the conductors
What is the energy stored in charged capacitor? (3 formulaes)
U=½Q^2/C
U=½QV
U=½CV^2
Give the principle of the capacitance.
The principle of the capacitance states that if an uncharged conductor is placed near the charged conductor than it’s capacitance rises.
Give formula of energy density of an electric field.
Ue=½ε0 E^2
What is energy density?
Energy stored per unit volume in a body
What is the potential when charges are shared?
V=C1V1+C2V2/c1+c2
What is the work done when charges are shared?
W=½(C1V1+C2V2)^2 / C1+C2
What is the energy loss redistribution of the charges?
W loss=½C1C2/C1+C2*(V1-V2)^2
All dielectric materials are ____________.
Insulators
What is the induced charge on dielectric slab?
q=Q(1-1/K)
What is the capacitance of a dielectric partly filling the space?
C=ε0A/(d-t) + t/K
What is the capacitance for mixed dielectric slab?
C=ε0A/(t1/k1 + t2/k2)
What is the metallic slab independent of?
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.
What is the filed inside dielectric?
E=E0/K
What are the types of molecules inside dielectric?
Polar molecules
The ______ necessary to cause the breakdown of a dielectric measures its _______.
Potential gradient, dielectric strength
What is the unit of dielectric strength.
kV/mm
What does breakdown of voltage depends on?(2 points)
nature of dielectric and geometry of capacitor
