Power Dissipation Calculator

Resistors turn electrical energy into heat at this rate.

How the Math Works

The Power Dissipation Calculator uses the fundamental formula P = I² × R to determine how much electrical power is converted to heat in a resistor. This equation states that power (measured in watts) equals the square of the current flowing through the circuit (measured in amperes) multiplied by the resistance value (measured in ohms). Squaring the current emphasizes that power increases dramatically with higher currents, making current a critical factor in power calculations. This relationship stems from Joule's Law, which describes how electrical energy transforms into thermal energy in resistive materials.

Practical Applications

To use this calculator, simply enter the current in amperes and the resistance in ohms, then square the current value and multiply by the resistance. For example, if you have 0.5 amps flowing through a 100-ohm resistor, the calculation would be 0.5 ² = 0.25, then 0.25 × 100 = 25 watts of power dissipated. This calculation is essential when designing circuits to ensure your resistors can handle the power they'll encounter without overheating or failing, as resistors are rated by their maximum power dissipation capacity.

Day-to-Day Use

Understanding power dissipation helps you make informed decisions about electronic components in everyday devices. When replacing a burned-out resistor in a radio, printer, or other appliance, you need to select one that can dissipate the same amount of power to prevent immediate failure. This knowledge also helps explain why electronic devices feel warm during use - all that electrical power is being converted to heat. By calculating power dissipation, you can choose appropriately rated components, avoid costly equipment failures, and ensure your DIY electronics projects operate safely and reliably.

Worked example

2 A through 10 Ω → 40 W.

FAQ