We previously explained that George Simon’s Ohm experimentally observed the behaviour of voltage and current on a resistor. His basic analysis formed the Ohm’s Law statement which is given here:

“The amount of current flowing through any component is¬†directly proportional to the voltage applied across its ends, provided that resistance is constant”.

Explanation of term Resistance is constant

The terms resistance is constant means that we are performing our analysis on the same resistor.

Here few examples are provided to illustrate the above statement in an easy manner.

Example 1: A 1k ohm resistor connects in series with a variable voltage source. Calculate the values of current for 1,3,5,8 and 10V. Also, compare the current values for 2k and 5k resistors at 1V.


For 1k resistor:

–> 1V; I = V/R = 1mA

For 3V; I = 2mA

For 5V; I = 5mA

For 8V; I = 8mA

For 10V; I = 10mA

Our R in above case was 1k (constant).

Now by replacing 2k and 5k resistors at 1V.

First for 1V; I = 1V/2k  = 0.5 mA

and for 5k resistor; I = 1V/5k = 0.2 mA

After looking at two lines one can understand that by change value of resistance from 2 to 5k the value of current dropped down from 0.5mA to 0.2mA. This proves the basic Ohm’s Law statement.