Ohm's Law in Practice
V = I × R. This simple linear equation governs the vast majority of DC circuit behavior.
However, temperature coefficients mean resistance is rarely static. A copper trace increases in resistance by 0.39% for every degree Celsius rise, a figure cited in standard IPC-2152.
Key Specifications Data
| Variable | Unit | Symbol | Measurement Tool |
|---|---|---|---|
| Voltage | Volts (V) | V or E | Voltmeter (Parallel) |
| Current | Amperes (A) | I | Ammeter (Series) |
| Resistance | Ohms (Ω) | R | Ohmmeter (Unpowered) |
Frequently Asked Questions
Does Ohm's law apply to AC circuits?
Yes, but resistance is replaced by impedance (Z), which includes the effects of capacitance and inductance at specific frequencies.
Why doesn't my LED follow Ohm's law?
LEDs are non-linear semiconductor devices. Their current increases exponentially once the forward voltage threshold is reached.
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