Ohm's Law

Ohm's Law defines the linear relationship between voltage, current, and resistance in an electrical circuit. Formulated by Georg Simon Ohm in 1827, it states that the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance.

Mathematical Formulas

Ohm’s Law is expressed using three equivalent formulas:

• V = I × R → Voltage (V)

• I = V / R → Current (A)

• R = V / I → Resistance (Ω)

where:

• V: Voltage in volts

• I: Current in amperes

• R: Resistance in ohms

Example

A circuit has a resistance of 100 Ω and a voltage of 12 V:

I = V / R = 12 / 100 = 0.12 A = 120 mA

Applications

Ohm’s Law is fundamental to circuit design and analysis:

• Low-voltage electronics: Sizing resistors, understanding power consumption

• Power systems: Calculating current flow and voltage drops

• Electrical safety: Ensuring components operate within rated limits

• Education: Basic concept in electronics training and certification

Limitations

Ohm’s Law applies only to ohmic (linear) components. It does not hold for non-linear elements such as:

• Diodes

• Transistors

• Thermistors

In these cases, resistance depends on voltage, temperature, or current.