Electrical Resistance - Implications

Electrical Resistance











































If one volt of potential difference across a device causes on ampere of current to flow, then the device has a resistance of

1ohm = 1 = 1V/A

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Often the current through an object is proportional to the potential difference across it over a wide range of values.

The resistance is then a constant and the object is said to obey Ohm's Law.

V = IR = I times a constant

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Ohm's Law is not exact. Even a metal wire shows variable resistance when enough current flows through it to heat it up.

Many useful devices show extreme departures from Ohm's Law.

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Large currents move ions to where they should not be, disrupting bodily processes.
0.001A --- tingle
0.01A --- pain, convulsion
0.1A --- death (heart fibrillation)

Most of your electrical resistance is in your skin and varies from 500 ohms (clean) to several million ohms (dirty).

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