Ohm's Law. The potential difference between any two points
in a conductor is directly proportional to the current flowing through
it. (This only holds true for an ohmic material. Non-ohmic materials
do not display a direct relationship.)
V = IR
where V is the potential difference
measured in volts, I is the current
measured in amperes and R is
the resistance measured in ohms. Thus,
1 ohm = 1 volt / ampere.
The symbol used for the ohm is the Greek letter Omega
Increased resistance in an electric circuit decreases conductance.
Resistance and conductance are inversely related. The resistance
of a cylindrical resistor depends on its length, its cross-sectional area,
its temperature and the resistivity of the material. Resistance is directly
proportional to the length of the conductor and varies inversely with
its cross-sectional area. Resistance usually increases with temperature.
Some materials exhibit superconductivity (i.e., resistance drops to zero)
at lower temperatures. (Materials become superconductive at different
temperatures.) Resistance depends on the resistivity of the material.
The resistivity is defined as the resistance of a cylinder of the material
1 meter long with a cross-sectional area of
1 m2. Resistivity varies with
temperature. It is measured in