OHM'S LAW - DEFINITION
concept
According to Ohm's law the electrical resistance of a conductor to the passage of current is equal to the potential difference , V divided by the electric current I.
VERIFYING OHM'S LAW - EXAMPLE
Let resistance used for verification be R. MAKE a circuit of R, VOLTMETER and ammeter measuring voltage and current through R, rheostat (variable resistor), and a cell. Connect the components properly. Note down VALUES of voltage and current shown by voltmeter and ammeter. Repeat the above for different values of Rheostat. Record data in a tabular FORMAT and calculate
I
V
​
for each case. Its should be approximately same. Plot V v/s I on a graph paper. A straight line is obtained whose slope equals resistance.
LIMITATIONS OF OHM'S LAW - DEFINITION
concept
The limitations are:
V ceases to be proportional to I.
The relation between V and I depends on the sign of V. In other words, if I is the current for a certain V, then reversing the direction of V keeping its magnitude FIXED, does not produce a current of the same magnitude as I in the opposite direction. This happens for example in case of a diode.
The relation between V and I is not unique. i.e. there is more than one value of V for the same current I. A material exhibiting such behaviour is GaAs.