Ohm's Law Calculator | Voltage, Current, Resistance, Power

📖 How to Use This Ohm's Law Calculator

Select what you want to calculate - Voltage (V), Current (I), Resistance (R), or Power (P).

Enter the known values - For voltage: current and resistance. For current: voltage and resistance. For resistance: voltage and current. For power: voltage and current.

Click "Calculate" - Get your result with a complete step-by-step solution.

⚡ Understanding Ohm's Law

Ohm's Law is a fundamental principle in electrical engineering that describes the relationship between voltage, current, and resistance in an electrical circuit. It states that the current through a conductor between two points is directly proportional to the voltage across the two points, provided the temperature remains constant.

The law is expressed by the equation: V = I × R, where V is voltage in volts, I is current in amperes, and R is resistance in ohms.

📊 Ohm's Law & Power Formulas

Ohm's Law:
V = I × R | I = V / R | R = V / I

Power Formulas:
P = V × I | P = I² × R | P = V² / R

Where: V = Volts, I = Amperes, R = Ohms, P = Watts

🔬 Real-World Applications

Household Circuits: 120V/240V systems, circuit breaker sizing
LED Resistor Calculation: Determining correct resistor for LEDs
Battery Life: Calculating current draw and runtime
Power Supplies: Designing and testing power supplies
Electrical Safety: Understanding short circuits and overcurrent protection
Audio Equipment: Matching speakers and amplifiers (impedance)

💡 Common Electrical Values

Household outlets (US): 120V, 15-20A max (1800-2400W)
Household outlets (EU/UK): 230V, 13-16A max (3000-3680W)
USB Charger: 5V, 1-3A (5-15W)
Car Battery: 12V, 100-500 CCA
LED (typical): 2-3V, 20mA (0.04-0.06W)
Human body resistance: ~1kΩ to 100kΩ (wet vs dry skin)

📏 Resistor Color Code Guide

Black: 0 | Brown: 1 | Red: 2 | Orange: 3 | Yellow: 4
Green: 5 | Blue: 6 | Violet: 7 | Gray: 8 | White: 9
Gold: ±5% tolerance | Silver: ±10%

❓ Frequently Asked Questions (FAQ)

What is the formula for Ohm's Law?

Ohm's Law states that V = I × R. Voltage equals current multiplied by resistance. This relationship is fundamental to understanding how electrical circuits work.

How do I calculate power using Ohm's Law?

Power can be calculated using P = V × I (voltage × current). You can also use P = I² × R or P = V² / R, depending on which values you know.

What is the difference between AC and DC in Ohm's Law?

Ohm's Law applies to both AC and DC circuits. For AC circuits, you use RMS (Root Mean Square) values for voltage and current. Impedance (Z) replaces resistance for AC circuits with capacitors/inductors.

What is the unit of resistance?

Resistance is measured in Ohms (symbol: Ω). One Ohm is the resistance that allows one Ampere of current to flow when one Volt is applied.

What is a short circuit?

A short circuit occurs when resistance becomes very low (approaching zero), causing extremely high current flow according to I = V/R. This can cause overheating, sparks, and fire hazards.

Does Ohm's Law apply to all materials?

Ohm's Law applies to "ohmic" materials (metals, most conductors) where resistance is constant. Non-ohmic materials (semiconductors, diodes) have non-linear voltage-current relationships.