Class notes Physics Physics : Textbook For Class Xi

These topics are important for understanding capacitors, so make sure to
pay attention.



Agenda

Electrostatic potential energy

Electrostatic potential

Electrostatic potential for dipole and continuous bodies

Relation between electric field and potential

Today’s lecture will be brief, but it lays the foundation for understanding
capacitors. If you miss this lecture, you may struggle with capacitors later
on. So, stay tuned till the end!



Electrostatic Potential Energy

Let’s start with the concept of electrostatic potential energy. We have a
source charge and a small test charge at an infinite point. The source charge
wants the test charge to come closer, but the child playing a game is not
listening. So, the mother asks an external agent to bring the child to a point
inside the electrostatic field. The external agent does this work slowly, so the
velocity of the charge remains constant and there is no change in kinetic
energy. The work done by the external agent is stored as potential energy in
the system. This potential energy is known as electrostatic potential energy.



Electrostatic Potential

The electrostatic potential energy is defined as the work done in bringing a
charge from infinite position to a point in the electrostatic field. It is a scalar
quantity and depends on the charge configuration. We can calculate the
potential energy for a single charge or a system of charges using the
formula:



U = k * q1 * q2 / r

Where U is the electrostatic potential energy, k is the electrostatic constant,
q1 and q2 are the charges, and r is the distance between them.