**Electrostatic Potential and Capacitance – Notes **

**Potential energy in an external field**

Electrostatic potential energy of a system of charges is expressed as:

U = U_{12} +U_{23}+ +U_{13}

Electron volt is defined as the kinetic energy gained by an electron when accelerated under a potential difference of one volt.

Electrostatic potential energy in the system of two charges is expressed as:

U = q_{1} V(r_{1}) + q_{2} V(r_{2}) + 1/4πε_{0 }(q_{1} q_{2}/r_{12})

The electrostatic potential energy of the system can be written as:

= – (pE COS ⍬) – 1/4πε_{0} (q^{2}/2a)

**Electrostatic potential and potential due to a point charge**

The electric potential (V) at any point in the electric field of a charge configuration is equal to the work done to bring a unit positive charge from infinity to that point in the electric field.

The electric potential (V) at a point is expressed as: V= 1/4πε_{0 }(Q/r)

The electric potential V is a scalar quantity.