Give information about Potential Difference (p.d.) in detail.
Answers
Potential difference
In practice when we consider the flow of current between two points A and B of an electric circuit, we consider only the flow of charge between te two points A and B, therefore it is not necessary to know the exact potential at each point A and B. It is sufficient to know the potential difference (abbreviated as p.d.) between the two points A and B. Using the definition of potential at a point, the potential difference between two points can be defined as follows :
The potential difference (p.d.) between two points is equal to the work done per unit charge in moving a positive test charge from one point to the other.
It is a scalar quantity.
If W joule of work is done in moving a test charge Q coulomb from a point A to the point B, the potential difference between the two points A and B is
VA - VB = W/Q
(Note : The potential difference between two points in an electric circuit is measured by a voltmeter which is connected across those points in parallel with the circuit, taking care that the +ve marked terminal of voltmeter is connected to the higher potential point.)
Unit of potential difference
Potential difference (p.d.) is also expressed in volt (V). The potential difference between two points is said to be 1 volt if the work done in moving 1 coulomb charge from one point to other is 1 joule, i.e.,
1 volt = 1 joule ÷ 1 coulomb = 1 J C^-1