## ELECTROSTATIC POTENTIAL AND CAPACITANCE

## Electrostatic force :

**Electrostatic force**is a conservative force. It’s an attractive or repulsive force between two electrically charged objects.

## Potential at a point:

**Potential at a point**is the work done per unit charge (by an external agency) in bringing a charge from infinity to that point. If potential at infinity is chosen to be zero; potential at a point with position vector

**r**due to a point charge

**Q**placed at the origin is given is given by

## The electrostatic potential at a point:

**The electrostatic potential at a point**with position vector

**r**due to a point dipole of dipole moment

**p**placed at the origin is

For a charge configuration with position vectors the potential at a point

**P**is given by the superposition principle,
Where is the distance between and

**P**, as and so on.## Equipotential surface:

An

**Equipotential surface**is a surface over which potential has a constant value.## Potential energy:

**Potential energy**stored in a system of charges is the work done (by an external agency) in assembling the charges at their locations.

Potential energy of two charges at is given by

Where is distance between .

## Capacitor:

**A capacitor**is a system of two conductors separated by an insulator. Its capacitance is defined by,

**C = Q/V**

where,

**Q**and

**–Q**are the charges on the two conductors and

**V**is the potential difference between them.

The unit of capacitance is farad.

For a parallel plate capacitor (with vacuum between the plates).

Where

**A**is the area of each plate and d is the separation between them.

## Combination of Capacitors:

- For capacitors in the series combination, the total capacitance
**C**is given by

- In the parallel combination, the total capacitance
**C**is:

Where are individual capacitances.

## Energy stored in Capacitor:

The energy

The electric energy density (energy per unit volume) in a region with electric field is

**U**stored in a capacitor of capacitance**C**, with charge**Q**and voltage**V**isThe electric energy density (energy per unit volume) in a region with electric field is

Electrostatic potential | Potential due to a point charge |

Potential due to an electric dipole | |

Potential due to system of charges | |

Equipotential surfaces | Properties |

Relation between electric field and potential | |

Potential energy of a system of charges | Potential energy of a single charge |

Potential energy of a system of two charges in an external field | |

Potential energy due to dipole in an external field | |

Electrostatics of conductors | Results of electrostatics of conductor |

Dielectrics and polarisation | Polar and non-polar dielectrics |

Capacitors and capacitance | |

Capacitors and capacitance | Parallel plate capacitor |

Effect of dielectric on capacitance | |

Combination of capacitors | Effective capacitance of two capacitors (a) in series combination and (b) in parallel combination |

Energy stored in a capacitor | |

Numericals | Concept based problems |