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Introduction to electric potential and potential difference :
Quantitative Definition of Potential :
We consider the process of depositing an electric charge (say positive charge) on a body. This is called charging the body. If we deposit some more charge of the same kind on that body, this charge will experience a force of repulsion due to the like charges already present on the body. Some work has to be done to overcome this force of repulsion. The work done on the charge in the process of charging gets stored as potential energy of charges.
Electric Potential and Potential Difference : Formula
The potential energy per unit charge is called electric potential, i.e.,
Electric potential = Electric potential Energy / Charge
or Work done / Charge
If W is the amount of work done on the charge q in the process of charging a body, then potential V is given by
V = W/q
1. Potential due to a positive charge is positive.
2. Potential due to a negative charge is negative.
3. Electric potential of earth is taken to be zero.
Unit of potential : In S.I. system, unit of potential is volt, named after Alessandro Volta.
Potential of a body is said to be one volt if one joule of work is done in charging it with one coulomb of positive charge, i.e.,
1 volt = 1 joule / i coulomb
or 1 V = 1J / 1C = 1 JC-1
Electric potential is a scalar quantity.
Electric Potential and Potential Difference
Quantitative Definition of Potential Difference
The electric potential difference between two points say A and B in an electric circuit on a current carrying conductor is defined as the amount of work done in moving a unit charge from point A to point B. Let VA be the potential at point A, VB be the potential at B, such that VA > VB and WAB be the work done in moving the charge Q from point A to point B. Then, the potential difference between the points A and B is given by
ΔV = VA - VB = WAB/Q
Unit of potential difference : S.I. unit of potential difference is also volt (V).
Potential difference between two points in a current carrying conductor is said to be 1 volt if 1 joule of work is done in moving a charge of 1 coulomb from one point to another. Thus,
1 volt (V) = 1 joule (J) / 1 coulomb (C)
or 1 V = 1 JC-1
Potential difference is a scalar quantity. Potential difference is measured by an instrument called voltmeter.