Enter any two values to calculate the rest
Ohm's Law is the most fundamental principle in circuit analysis, discovered by German physicist Georg Simon Ohm in 1827. It describes the linear relationship between voltage, current, and resistance: the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance.
V = I × R — Voltage (V) = Current (A) × Resistance (Ω)
P = V × I — Power (W) = Voltage (V) × Current (A)
P = I² × R — Power = Current² × Resistance
P = V² ÷ R — Power = Voltage² ÷ Resistance
Selecting Resistors: In an LED circuit, calculate the current-limiting resistor. For a red LED (2V forward voltage) with 5V supply and 20mA current: R = (5-2)/0.02 = 150Ω.
Power Supply Selection: Choose the right power adapter based on device voltage and power requirements. A 12V/5A supply delivers 60W maximum.
Safety Assessment: Calculate power dissipation in circuit components to ensure they stay within rated limits and prevent overheating.
1. Enter any two known values in the four input fields (Voltage V, Current A, Resistance Ω, Power W).
2. The tool automatically calculates and displays all unknown parameters.
3. Results use engineering units for readability (e.g., kΩ, mA, mW).
4. Click "Reset" to clear all inputs.
Tip: Use decimal values like 0.001 for 1mA or 1000 for 1kΩ — the tool handles unit formatting automatically.
Limitations: Ohm's Law applies to linear components (pure resistors). Non-linear devices like diodes and transistors have non-linear V-I relationships. For AC circuits with capacitors and inductors, use impedance (Z) instead of resistance.
Power Loss: Resistive power loss (Joule heating) P = I²R. In long-distance power transmission, higher voltage reduces line current, minimizing I²R losses—this is why power grids use high-voltage transmission.
Safety: Always ensure circuit components operate within their rated values. A resistor's power rating (e.g., 1/4W, 1/2W) must exceed actual power dissipation to prevent overheating damage.
Ohm's Law is a fundamental principle in electrical engineering, discovered by German physicist Georg Simon Ohm in 1827. The formula is V = I × R, where V is voltage (volts), I is current (amperes), and R is resistance (ohms). The power formula P = V × I calculates power consumption in a circuit.
According to Ohm's Law, voltage V = I × R. If you know the current (amperes) and resistance (ohms) in a circuit, multiply them to get voltage (volts). For example, 2 amps through a 5 ohm resistor gives 2 × 5 = 10V. You can also use P = V × I and rearrange as V = P ÷ I.
Using Ohm's Law, resistance R = V ÷ I. If you know voltage (volts) and current (amperes), divide voltage by current to get resistance (ohms). For example, 12V with 3A current gives 12 ÷ 3 = 4Ω. Resistance can also be calculated using R = V² ÷ P.
Electrical power P = V × I (volts × amperes), measured in watts (W). You can also use P = V² ÷ R or P = I² × R. For example, 5V at 2A gives 5 × 2 = 10W. Understanding power is crucial for selecting proper wire gauges and circuit protection.
Ohm's Law is fundamental to electronics and electrical engineering. Whether repairing appliances, designing circuit boards, choosing power adapters, or learning electronics, Ohm's Law helps you calculate circuit parameters to ensure safe operation and prevent overload damage.
The basic Ohm's Law formula V=IR applies to DC circuits and purely resistive AC circuits. For AC circuits with capacitors and inductors, impedance (Z) replaces resistance (R): V = I × Z. This calculator is designed for DC circuits and resistive AC circuits.