Current and Power at 3 V and 1 Ω
Use the calculator below to solve for any other combination.
Power
9 W
Example
With 3V and 1Ω, the current is 3A and the power dissipated is 9W (P = V × I).
Voltage
3 V
Current
3 A
Resistance
1 Ω
Voltage vs. current at 1Ω
What Is Ohm's Law?
Ohm's Law describes the relationship between voltage, current, and resistance in an electrical circuit: voltage equals current multiplied by resistance (V = IR). It's one of the most fundamental relationships in electronics, letting you calculate any one of the three quantities given the other two.
Combined with the power equation (P = VI), Ohm's Law lets you solve for all four key electrical quantities — voltage, current, resistance, and power — from any two known values, which is exactly what this calculator does.
Power at Different Resistances
Holding your voltage constant at 3V, here's how power changes as resistance changes — power drops sharply as resistance increases (P = V² ÷ R).
| Resistance | Current | Power |
|---|---|---|
| 1Ω | 3 A | 9 W |
| 2Ω | 1.5 A | 4.5 W |
| 5Ω | 0.6 A | 1.8 W |
| 10Ω | 0.3 A | 0.9 W |
| 20Ω | 0.15 A | 0.45 W |
| 50Ω | 0.06 A | 0.18 W |
| 100Ω | 0.03 A | 0.09 W |
The Ohm's Law & Power Formulas
Any two known quantities among voltage, current, and resistance let you solve for the third using V = IR (rearranged as I = V/R or R = V/I), and power can then be found from any pair of the three using whichever form of the power equation is most convenient.
Why Resistance and Power Have an Inverse-Square Relationship
At a fixed voltage, power equals voltage squared divided by resistance (P = V²/R) — so doubling resistance cuts power to a quarter, not just half. This is why small changes in resistance (like a partially failing connection) can cause outsized changes in heat and power dissipation.
Ohm's Law Assumes a "Linear" Component
Ohm's Law applies precisely to resistors and other "ohmic" components whose resistance stays constant regardless of voltage or current. Many real components — diodes, transistors, light bulb filaments that heat up — are "non-ohmic," meaning their resistance changes with operating conditions, so Ohm's Law is an approximation for them at best.
Practical Uses of Ohm's Law
Ohm's Law is used to size resistors for LED circuits, calculate fuse and wire ratings, verify that a power supply can handle a given load, and troubleshoot circuits by checking whether measured voltage, current, and resistance values are mutually consistent.
Example — Your Current Inputs
With 3V and 1Ω, the current is 3A and the power dissipated is 9W (P = V × I).
Additional Example — Sizing an LED Resistor
An LED needing 20mA (0.02A) at a 2V forward voltage, powered from a 9V supply, needs a resistor to drop the remaining 7V: R = V/I = 7 ÷ 0.02 = 350Ω. The resistor dissipates P = VI = 7 × 0.02 = 0.14W, well within a standard 0.25W resistor's rating.
About These Parameters
- Known Values
- Choose whichever two quantities you already know from a datasheet, measurement, or circuit design — the calculator solves for the remaining two automatically.
- Voltage, Current & Resistance
- Voltage is measured in volts (V), current in amps (A), and resistance in ohms (Ω). Power, always computed as an output, is measured in watts (W).
Frequently Asked Questions
What is the Ohm's Law triangle?
A memory aid that arranges V, I, and R in a triangle — covering the quantity you want to solve for reveals whether to multiply or divide the other two, e.g. covering V shows I × R.
Does Ohm's Law apply to AC circuits?
The basic form applies to purely resistive AC circuits. Circuits with capacitors or inductors require the AC equivalent using impedance instead of plain resistance, which this calculator does not model.
Why does my calculated resistance not match the component's rating?
Real components have manufacturing tolerances (often ±5% or ±10%), and resistance can shift slightly with temperature — small deviations between a calculated and measured value are normal.