A source of potential difference V volt sends current I ampere in a circuit for time t second. Write expressions for
- electrical energy supplied by the source and
- electrical power spent by the source.
Potential difference V is the work done in moving a unit charge
∴ Work was done in moving a charge Q through the pot. diff. V = QV
i.e. W = QV
but = `"Q"/"t" = "I"` or Q = It
∴ W = VIt
Work done = Electrical energy
(a) ∴ Electrical energy = VIt is the expression
(b) Power is the rate of doing W
P = `"W"/"t" = "VIt"/"t" = "VI"`
P = VI is the expression.