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Electronics
Ohm's law
Calculate resistance and power from voltage and current using Ohm's law. The foundation of any electronics or Arduino project.
Inputs
V
A
In amperes. 20 mA = 0.02 A.
Result
Resistance
250Ω
Power0.1 W
How it works
What it is
Ohm's law links voltage (V), current (I) and resistance (R): V = R × I. It's the starting point for sizing any component in a circuit.
Why power matters
Power (P = V × I) tells how much heat a component dissipates. Picking a resistor rated below what's needed makes it burn out. Always leave headroom.
Formula
R = V / I • P = V × IMore in Electronics
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