Electric Potential

Just as a body raised above the ground gravitational potential energy, similarly, a charged body has electric potential energy.When a body is charged, work is done in charging the body. This work done is stored in the body in the form of electric potential energy. The charged body has the capacity to do work by moving other charges either by attraction or repulsion. Quantitatively, electric potential is defined as under :
The electric potential at a point is the electric potential energy per unit charged.
Electric potential, V = Electric potential energy /Charge = W/C

The SI unit of energy or work is 1J and that of charge is 1C so that SI unit of electric potential is 1J/C which is also called 1 volt.

Thus when we say that electric potential at a point is 10V, it's means that if we place a charge of 1C at that point, the charge will have electric potential energy of 10J. Similarly, if we place a charge of 2C at that point, the charge will have electric potential energy of 20J. Note that potential energy per unit charge (i.e. electric potential ) is 10V.

Potential Difference

As the units of measure for Potential Difference are volts, potential difference is mainly called voltage. Individual voltages connected in series can be added together to give us a “total voltage” sum of the circuit as seen in the resistors in series tutorial. Voltages across components that are connected in parallel will always be of the same value as seen in the resistors in parallel tutorial, for example.

For series connected voltages:

For parallel connected voltages:

By using Ohm’s Law, the current flowing through a resistor can be calculated as follows:

Calculate the current flowing through a 100Ω resistor that has one of its terminals connected to 50 volts and the other terminal connected to 30 volts.

Voltage at terminal A is equal to 50v and the voltage at terminal B is equal to 30v. Therefore, the voltage across the resistor is given as:

VA = 50v, VB = 30v, therefore, VA – VB = 50 – 30 = 20v

The voltage across the resistor is 20v, then the current flowing through the resistor is given as:

I = V_AB ÷ R = 20V ÷ 100Ω = 200mA