Power: The power of a process is the amount of some type of energy converted into a different type divided by the time intervalin which the process occurred:
โฆ.. (1)
The SI unit of power is the watt (W).
Because the potential difference across a resistor is given bywe can express the power delivered to a resistor as
โฆ.. (2)
The energy delivered to a resistor be electrical transmission appears in the form of internal energy in the resistor.
Electrical resistance: The electrical resistance R of a resistive circuit element depends on its geometric structure (its length L and cross-sectional area A) and on the resistivityof the material of which it is made: