Ohm's Law

Ohm's law applies to electric conduction through conductors and may be stated as follows:-


‘The ratio of potential difference (V) between any two points on a conductor to the current (I) flowing between them, is constant, provided the temperature of the conductor does not change.’


In other words V/I = constant

or V /I = R

Where R is the resistance of the conductor between the two points considered

Put in another way, it simply means that provided R is kept constant, current is directly proportional to potential difference across the ends of the conductor. For a constant value of R, if the value of V is increased, the value of I increases; if V is decreased, then I decreases.  Also notice that if V is constant and R is increased, I decreases.  Similarly, if V is constant and R is decreased, I increases.

Figure show the current voltage relationship for R=10 ohm.

Material that obeys Ohm's Law is called 'ohmic' or 'linear'  because the potential difference across it varies linearly with the current. However this linear relationship between V and I does not apply to all non-metallic conductors.