Chapter Electrostatics in Class 12
There are two chapters in the unit Electrostatics. They are: Chapter 1: Electric charges and fields Chapter 2. Electrostatic potential and capacitance The important topics of the two chapters are as follows:
CBSE class 12 physics Chapter 2 Electrostatic Potential and Capacitance

Electrostatic Potential

  • When a charge with a positive unit travel from point A to another point B against an electrostatic force in an electric field, the difference of electrostatic potential between point A and point B will be the amount of work done to shift the charge from point A to point B with zero acceleration.
  • The formula of electrostatic potential is as follows:
Electrostatic potential (V0 = Work done (W)/Charge (q)
  • Volt (V) stands for the Si unit of electrostatic potential.
  • The amount of work that is done to move a charge of 1 coulomb in an electrostatic field against an electrostatic force is 1J. Thus, the electrostatic potential is 1JC-1.

Electrostatic potential difference

  • When a charge with a positive unit travel from say point A to another point say point B against an electrostatic force in an electric field, then the difference of electrostatic potential between point A and point B will be the amount of work done to shift the charge from point A to point B with zero acceleration.
  • The formula of electrostatic potential difference is as follows:
  • There is another formula of electrostatic potential difference which is as follows:
It is possible to find out the potential difference between point A and point B with the line integral of the electric field from point A to point B.
  • When a point with charge q is at any point and the distance is r, then the electrostatic potential can be calculated as:
  • When the point charge is positive, then the electric potential at that point is positive. When the point charge is negative, then the electric potential at that point is negative.
  • A positive charge moves from higher potential to lower potential when it is placed in an electric field. Negative charge happens to move from lower potential to higher potential when it is placed in an electric field.
The formula of electrostatic potential due to an electric dipole The formula of electrostatic potential due to an electric dipole at point P is given as:
The formula of electro potential of a thin charged spherical shell
  • The formula of the electrostatic potential at a point P which is inside a thin charged spherical shell carrying charge q and radius R is given as:
  • The formula of the electrostatic potential at a point P which is on the surface of a thin charged spherical shell carrying charge q and radius R is given as:
  • The formula of the electrostatic potential at a point P which is outside the thin charged spherical shell carrying charge q and the distance between the point P outside the shell and the center of the shell r is given as:
Electrostatic potential energy
  • When a charge q moves from one point to another, the work that is done by the charge q is kept as electrical potential energy.
  • The formula of electrostatic potential energy in a system which have two charges namely q1 and q2 is as follows:
The above given are some important concepts and formulas which are important to the students while studying the electrostatic potential and capacitance class 12. Chapter 1- Electric charges and fields Definition of Electric charge Charge is defined as that property which is related to matter as a result of which it produces and experiences electrical and magnetic effects. Types of charge There are two types of charge in nature. They are; 1.Positive charge 2.Negative charge Charges which have same electrical sign repel each other. Charges which have opposite electrical signs attract each other. Point charge Point charge is that charge in which the spatial size is not noticeable as compared to other distances. Properties of charge
  • Charge is a scalar quantity: This means that charges can be added or subtracted algebraically.
  • Charge is transferrable: When a charged body comes into contact with an uncharged body, then the uncharged body gets charged as a result of transfer of electrons from the charged body to the uncharged body.
  • Charge is always found to be associated with mass: Charge can never occur without mass whereas mass can exist without charge.
  • Charge is conserved: Charge cannot be created nor be destroyed.
  • Invariance of charge: The numerical value of an elementary charge is not dependent on velocity.
  • Charge produces an electric field and magnetic field: When a charged particle is at a state of rest then it produces an electric field in the space surrounding it. But if the charged particle is in motion, then it produces both electric and magnetic fields.
Now, solve this question: 5×10^(5) lines of electric flux are entering in a closed surface and 4×10^(5) liner come out of the surface the charge enclosed by the surface is?