## Voltage, Current, and Resistance

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*:

(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

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