CBSE Class 12 Physics Notes Chapter 2 - Electrostatic Potential and Capacitance

What is Electrostatic?

The electrostatic potential is referred to the force which is external but conservative. It is the work done by an external force in bringing a charge s from a point r to a point p. It is the difference in the potential energy of charge s between initial and final points.

Potential

Potential of a point is referred to the work done per unit charge in bringing a charge from infinity to a certain point.

Equipotential surface

It is a type of surface over which potential has a constant value. When seen as a point charge, concentric spheres centered at a particular location of the charge are equipotential surfaces.

Potential Energy

The potential energy stored in a system is the work done by the external influence in organizing the charges in their locations.

Polarisation

The plates of a capacitor enclose a medium which can be filled with insulating substances, then the electric field due to the charged plates induces a net dipole moment in the dielectric. This gives rise to the field in the opposite direction.

Capacitor

A capacitor is a system of two conductors separated by an insulating material.

Important Question

  1. A spherical conductor has a charge of 4 × 10–8C distributed uniformly on its surface of radius 15 cm. Calculate the electric field just outside the sphere and at a point 15 cm from the center of the sphere.
  1. Find out the capacitance if the distance between the plates is reduced by half and the parallel plate capacitor has a capacitance of 20 pF (1pF = 10–12 F) with air between the plates.
  1. What is the total capacitance of the combination Three capacitors each of capacitance 20 pF are connected in series.

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Practise This Question

A compound microscope is used to enlarge an object kept at a distance 0.03m from it’s objective which consists of several convex lenses in contact and has focal length 0.02m. If a lens of focal length 0.1m is removed from the objective, then by what distance the eye-piece of the microscope must be moved to refocus the image