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Resistance
Resistance
is measured in Ohms (symbol W).
Resistance is a measure of
how much the current is slowed down.
The bigger the resistance, the smaller the current.
The very important equation
is an expression of Ohm's Law.
If the
resistance of a component is
constant (stays
the same)
for different values of V and
I,
then a plot (graph) of V against
I will be a straight line.
The gradient (slope) of the line
shows how big the resistance
is.
A test circuit is used to find a range of voltages and currents for a component.
Components which obey Ohm's
Law are Wires and Resistors.
A component will only obey
Ohm's Law at constant temperature
(meaning that the temperature must
not change).
In reality, an increase
in current through a component
will change its temperature (the temperature usually goes up),
and so Ohm's Law is only an approximation
but it works quite well for many
components.
The next page shows plots for
components which don't obey Ohm's
Law.
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Copyright © 2008 Dr. Colin France. All Rights Reserved.