Current through a 470Ω resistor at 9V
Worked answer for 9V applied across a 470Ω resistor, using Ohm's law (I = V/R) and power (P = V²/R).
Current 19.1 mA 9V ÷ 470Ω · dissipates 172 mW
| Voltage (V) | 9 V |
| Resistance (R) | 470Ω |
| Current I = V / R | 19.1 mA |
| Power P = V² / R | 172 mW |
Driving 9V through 470Ω gives 19.1 mA of current (I = V/R) and the resistor must dissipate 172 mW of heat (P = V²/R). Pick a resistor power rating comfortably above that figure.
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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.