Ohm's Law Calculator – Voltage, Current, Resistance
Calculate voltage, current, and resistance using Ohm's law
Table of Contents
How to Use
- Enter any two values: voltage (V), current (I), or resistance (R)
- Leave the value you want to calculate empty
- Click calculate to see all calculated values including power
- The calculator uses Ohm's law: V = I × R
What is Ohm's Law?
Ohm's law states that the voltage across a conductor is directly proportional to the current flowing through it, provided the temperature and other physical conditions remain constant. It's one of the fundamental principles of electrical engineering.
Named after German physicist Georg Simon Ohm, who discovered it in 1827, Ohm's law is expressed by the equation: V = I × R, where V is voltage, I is current, and R is resistance.
Ohm's Law Formulas
The basic equation can be rearranged to solve for any variable:
- Voltage: V = I × R
- Current: I = V / R
- Resistance: R = V / I
Power can also be calculated using:
- P = V × I
- P = I² × R
- P = V² / R
Units
Standard electrical units:
- Voltage (V): measured in Volts
- Current (I): measured in Amperes (Amps)
- Resistance (R): measured in Ohms (Ω)
- Power (P): measured in Watts
Applications
Ohm's law is fundamental in:
- Circuit design and analysis
- Electronic component selection
- Power supply design
- Troubleshooting electrical circuits
- Electrical safety calculations
- Battery and power management
- LED and resistor calculations
Frequently Asked Questions
- What is the relationship between voltage, current, and resistance?
- According to Ohm's law, voltage equals current multiplied by resistance (V = I × R). If you increase voltage while resistance stays constant, current increases. If you increase resistance while voltage stays constant, current decreases.
- Does Ohm's law apply to all materials?
- Ohm's law applies to linear, ohmic materials where resistance is constant. Some materials like semiconductors, diodes, and certain conductors have non-linear behavior and don't strictly follow Ohm's law.
- How do I calculate power from voltage and current?
- Power is calculated by multiplying voltage and current: P = V × I. You can also use P = I² × R or P = V² / R when you know resistance.
- What happens if I enter all three values?
- This calculator requires exactly two values. Enter any two of voltage, current, or resistance, and leave the third empty. The calculator will verify that the values satisfy Ohm's law.