Current through a 220Ω resistor at 9V
Worked answer for 9V applied across a 220Ω resistor, using Ohm's law (I = V/R) and power (P = V²/R).
Current 40.9 mA 9V ÷ 220Ω · dissipates 368 mW
| Voltage (V) | 9 V |
| Resistance (R) | 220Ω |
| Current I = V / R | 40.9 mA |
| Power P = V² / R | 368 mW |
Driving 9V through 220Ω gives 40.9 mA of current (I = V/R) and the resistor must dissipate 368 mW of heat (P = V²/R). Pick a resistor power rating comfortably above that figure.
Different values? Enter any two of voltage, current, resistance or power in the interactive tool:
Open the Ohm's Law Calculator →Disclaimer: This is a reference estimate using ideal Ohm's law. Real components have tolerance and self-heating; verify against your part's datasheet and power rating before building.