Electrical Laws
Ohm’s Law
Ohm’s law relates voltage, current and resistance in a linear conductor: the voltage across the resistance equals the current through it multiplied by the resistance. The same relationship can be rearranged as I = V ÷ R or R = V ÷ I. It is the starting point for almost every DC calculation, but it does not describe non-ohmic devices such as diodes or lamp filaments, whose resistance changes with operating point.
Ohm’s Law
V = I × R
Variables and units
| Symbol | Quantity | Unit |
|---|---|---|
| V | Voltage | V |
| I | Current | A |
| R | Resistance | Ω |
Conditions of application
Linear, time-invariant resistance; conventional current; the resistance is treated as constant over the operating range.
Worked example
Solved
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Solve V = I × R for voltage, current or resistance and check power.