The state of an ideal resistor is completely specified by the voltage
across it (call it
volts) and the current passing through
it (
amperes, or simply ``amps''). The ratio of voltage to
current gives the value of the resistor (
resistance in
Ohms). The fundamental relation between voltage and current in a
resistor is called
Ohm's Law:
where we have indicated also that the voltage and current may vary with time (while the resistor value normally does not).
The electrical power in watts dissipated by a resistor R is given by
where