What is the shape of equipotential surface for a given point charge q ?.

Equipotential surfaces are surfaces of constant scalar potential. They are used to visualise an n dimensional scalar potential function in n - 1 dimensional space. The gradient of the potential, denoting the direction of greatest increase, is perpendicular to the surface For a single, isolated point charge, the potential is inversely dependent upon the radial distance from the charge. Therefore, the equipotential surface for a single point charge is spherical, with the point charge at the centre.

Derive an expression for the energy stored in a capacitor. In what form is the energy stored in a charged capacitor?

The capacitor is a charge storage device. While charging the condenser, work has to be done to store the charges in a capacitor. This work done is stored as electrostatic potential energy in the capacitor. Let q be the charge and V be the potential difference between the plates of the capacitor. If a small dq is an additional charge given to the plate, then work done is dw = Vdq = q C dq where C = capacitance of the capacitor. Total work done to charge a capacitor is, ∫ dw = ∫ 0 C q c dq = 1 C ∫ 0 C dq = 1 2 q 2 C ............................................(1) This work done is stored as electrostatic potential energy U in the capacitor. Therefore, the energy is given by, E = 1 2 q 2 c = 1 2 CV 2 ( as q = CV ) . Therefore, the energy on a condenser is 1 2 CV 2 .

A parallel plate capacitor has a capacity of 6 μF (micro farad), with air in between the plates and 60 μF (Micro farad) capacitor. What is the dielectric constant ( K ) of the medium?

The capacitance of a capacitor when the dielectric constant K is introduced is C = K C 0 , where C 0 is the capacitance without dielectric constant. So, 60 = K × 6 K = 10

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 2 - Electrostatic Potential and Capacitance>Punjab Board-2019>Q 5

EASY

12th Punjab Board

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Draw equipotential surfaces for a positive point charge.

Important Questions on Electrostatic Potential and Capacitance

MEDIUM

12th Punjab Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 2 - Electrostatic Potential and Capacitance>Punjab Board-2019>Q 6

Define electric potential at a point in electrostatic field. Derive an expression for electric potential at a point due an electric dipole. What will be the value of electric potential at any point in the equatorial plane.