Relative potential is the voltage of one point in a circuit
with respect to that at another point (usually called the reference or common
point).
with respect to that at another point (usually called the reference or common
point).
Consider
the circuit shown in figure 1 below;
The most negative end-point C has been taken as the reference.
With respect to point C, both point A and B are positive though A is more
positive than B. The voltage of point B with respect to that of C. VBC
= +30V.
With respect to point C, both point A and B are positive though A is more
positive than B. The voltage of point B with respect to that of C. VBC
= +30V.
Similarly VAC = +(20+30) = +50V.
In figure 2 below,
The most positive end-point A has been taken as the reference
point. With respect to A, both B and C are negative though C is more negative
than B.
point. With respect to A, both B and C are negative though C is more negative
than B.
VBA= -20V, VCA = -(20+30) = -50V.
In figure 3 shown below,
The mid-point B has been taken as the reference point. With
respect to B, A is at a potential whereas C is at a negative potential. Hence,
VAB = +20V and
respect to B, A is at a potential whereas C is at a negative potential. Hence,
VAB = +20V and
VCB = -30V (of course, VBC = +30V).
It may be noted that any point in the circuit can be chosen as
the reference point to suit our requirements. This point is often called ground
or earth because originally, it meant a point in a circuit which was actually
connected to either for safety in power systems or for efficient radio
reception and transmission. Although, this meaning still exists, yet it has
become usual today for “ground” to mean any point in a circuit which is
connected to a large metallic object such as the metal chassis of a
transmitter, the aluminum chassis of a receiver, a wide strip of a copper whole
equipment. Sometimes, reference point is also called common point.
the reference point to suit our requirements. This point is often called ground
or earth because originally, it meant a point in a circuit which was actually
connected to either for safety in power systems or for efficient radio
reception and transmission. Although, this meaning still exists, yet it has
become usual today for “ground” to mean any point in a circuit which is
connected to a large metallic object such as the metal chassis of a
transmitter, the aluminum chassis of a receiver, a wide strip of a copper whole
equipment. Sometimes, reference point is also called common point.
The main advantage of using a ground system is to simplify our
circuitry by saving on the amount of wiring because ground is used as the return
path for many circuits. The three commonly used symbols for ground are shown in
figure 4 below.
circuitry by saving on the amount of wiring because ground is used as the return
path for many circuits. The three commonly used symbols for ground are shown in
figure 4 below.
