Understanding Ohm's Law: Definition, Formula, and Examples

Ohm’s Law states that the current through a conductor is directly proportional to the voltage across it, provided the temperature and other physical conditions remain constant. We can derive Ohm’s Law from the following data:

From the table, the ratio V/I has a constant value of 10. It’s crucial that the resistance (R) for this conductor remains constant even when V and I change proportionally.

Ohm’s Law

“Directly proportional” means doubling the voltage (V) doubles the current (I), trebling V trebles I, and so on.

In mathematical terms, Ohm’s Law can be written as:

$I \propto V$

Another way to express Ohm’s Law is to say that the resistance of a conductor remains constant as long as physical conditions stay the same. Conductors that obey Ohm’s Law are typically made of metals, carbons, and some alloys. These are known as ohmic conductors.

Conductors that don’t obey Ohm’s Law are called non ohmic conductors. Their resistance changes with voltage and current. Transistors are an example of non ohmic devices. The characteristic curve for an ohmic conductor is a straight line.