Current and Resistance

This lecture is based on Serway, Sections 27.4 and - 27.6.

Some materials become superconducting when their temperature drops below a certain point: their resistivity becomes zero
In the late 1980s, some researchers found materials which become superconducting at temperatures above 77 K -- that means that devices can be kept cool with cheap liquid nitrogen dewars
A resistor is a device which converts electric current into thermal energy

The power dissipated by a resistor is

            power = (current) * (voltage across resistor)

or, using Ohm's Law,

            power = (current)^2 * (resistance)

                  = (voltage across resistor)^2 / (resistance)

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