Ohm's Law Explained: Voltage, Current and Resistance

Understand the relationship between voltage, current and resistance with practical examples.

Ohm's Law describes the relationship between voltage (V), current (I) and resistance (R) for an ohmic component under the conditions where the relationship applies.

The relationship

V = I × R. From the same relationship, I = V ÷ R and R = V ÷ I.

Example

If a resistive load is 10 Ω and the applied voltage is 20 V, the current is 2 A.

Power

Electrical power can be related using P = V × I. Combining this with Ohm's Law gives other useful forms such as P = I²R.

Safety

These calculations are not a substitute for electrical design, protection selection or safe working procedures.