FORMULABOOKLET PHYSICS CLASS 12 CHAPTER CAPACITANCE Physics Formulas Class 12 Chapter- Capacitance 1. c = q/v where c = capacity of a condenser (farad) The capacity of a special conductor C = 4πε0R q-charge (coulomb), V-potential (volt) 2. C = ε0 - A/d Where c0 = capacity of a parallel plate capacitor (air is medium) A= π r2 for circular plates d = distance between the plates (m)
C = K ε 0 A/K(d - t) + t
V/Q = 1/C1 + 1/C2 + 1/C3
The ratio of potentials v1:v2:v3=
1/C = 1/C1 + 1/C2
i.e, Q = Q1 = Q2 = Q3
(a) ‘v’is the same across all the capacitors
4. In a series combination of ‘3’capacitors,
(c) Effective capacitance
Note:- If all are identical capacitors, then InC/Nparallel combination of ‘3’capacitors.
i.e., v = v1 = v2 = v3
V1 = C2/C1 + C2 ; V2 = (C1/C1 + C2)V
3. When a medium of dielectric constant ‘k’is placed between the plates than its capacity
ForC/Ntwo capacitors
1/C = 1/C1 + 1/C2 + 1/C3 + 1/C4+.........
The ratio of charges is 1 : 1: 1
(b)Total potential, v = v1 +v2 + v3
V = Q/C1 + Q/C2 + Q/C3
(a) Q is the same on all the capacitors
1/C = 1/C1 + 1/C2
ε 0 = Permittivity of free space (f/m)
U = 1/2 CV2 = 1/2 QV = 1/2 Q2/C
5. Energy stored in a capacitor
● The capacity of a conductor is one farad when 1 coulomb of charge is added to the conductor to raise its potential by 1volt.
Note: If all are identical capacitors, Then C1 = C2 = C3 = C and CP3C, CPnC [for n capacitor]
Where C – Capacity of capacitor
The ratio of potentials is 1 : 1: 1
6. If a dielectric of ‘k’, thickness ‘t’is placed between the plates of a parallel plate capacitor then Its capacity is C = [ε0 A/(d - t) {1 + 1/t}]
● The capacity of conductors is the ratio of charge (q) on them to their potential (V). c = q/v
(b) Total charge, Q = Q1 + Q2 + Q3 = C1 : C2 : C3
Conceptual points
● Unit of capacity is coulomb/volt or farad.
FrequentlyAsked Question (FAQs)
Do follow NCERTSolutions for class 12 Physics prepared by the expert faculty of Physics Wallah. Students can also get the Important Questions for CBSE Class 12 Physics.
Q1. What is capacitance for class 12th?
(c) effective capacity, CP = C1+C2+C3
V – Potential, Q – Charge, U – Energy stored in J
Q4. What are the two types of capacitors?
Q6. What is a coulomb unit?
Q3. What is the formula for a capacitor?
Ans.The governing equation for capacitor design is C = εA/d. In this equation, C is capacitance; ε is permittivity, a term for how well dielectric material stores an electric field;Ais the parallel plate area, and d is the distance between the two conductive plates.
Ans. Capacitors are divided into two mechanical groups: fixed capacitors with constant and variable capacitors with variable (trimmer) or adjustable (tunable) capacitance values.The most important group is the fixed capacitor.
Q2. What is the SI unit of capacitance?
Q5. Where are capacitors used?
Ans.The SI unit of capacitance is farad.
Ans. Coulomb (represented by C) is a standard electric charge unit in the International System of Units (SI). It is an infinite number; share this feature with the mole.Avalue of 1 C equals approximately 6.24 x 1018, or a quintillion 6.24.
Ans. Capacitors are very popular in many systems, such as power circuits, electronic circuits, and power supply units. The capacitor is called the Big Three Passive Components and coil resistors, the basics of electrical circuits.
Ans.The capacitance (C) of a capacitor is defined as the charge ratio (Q) given the potential difference (V) applied to all conductors, i.e., C = Q / V.The SI unit of capacitance is the farad (F).
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