Ohm's Law Calculator

Calculate voltage, current, resistance, and power using Ohm's Law and power equations for electrical circuits.

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Ohm's Law

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points.

The mathematical equation is V = I × R, where:

  • V = Voltage in volts (V)
  • I = Current in amperes (A)
  • R = Resistance in ohms (Ω)

From this relationship, we can derive two other forms:

  • I = V ÷ R (Current = Voltage ÷ Resistance)
  • R = V ÷ I (Resistance = Voltage ÷ Current)

Circuit Diagram

A circuit diagram visualizes how voltage, current, and resistance interact in an electrical circuit.

+-VRI

A simple electrical circuit showing the relationship between voltage (V), current (I), and resistance (R).

Power Formulas

Power from Voltage and Current

P = V × I

Power (watts) = Voltage (volts) × Current (amperes)

Power from Current and Resistance

P = I² × R

Power (watts) = Current² (amperes) × Resistance (ohms)

Power from Voltage and Resistance

P = V² ÷ R

Power (watts) = Voltage² (volts) ÷ Resistance (ohms)

Ohm's Law Formula Wheel

V

I × R

I

V ÷ R

P

V × I

R

V ÷ I

Understanding the Formula Wheel

The Ohm's Law wheel is a visual aid that helps you remember how to calculate any electrical value when you know two others.

V

Voltage (V) = Current (I) × Resistance (R)

I

Current (I) = Voltage (V) ÷ Resistance (R)

R

Resistance (R) = Voltage (V) ÷ Current (I)

P

Power (P) = Voltage (V) × Current (I)

Practical Applications

Electronics Design

Used in designing circuits, determining component specifications, and ensuring electronic devices operate within safe parameters.

Battery Management

Calculating power consumption, battery life, and charging requirements for portable electronic devices.

Electrical Troubleshooting

Diagnosing issues in electrical systems by measuring and comparing actual values against expected values.

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Frequently Asked Questions

Find answers to common questions about Online Calculator.

Ohm's Law states that the voltage (V) across a conductor is directly proportional to the current (I) flowing through it, given a constant resistance (R). The formula is: V = I × R.

Use the formula: V = I × R. Example: If the current is 2A and the resistance is 5Ω, then voltage V = 2 × 5 = 10V.

Use the formula: I = V / R. Example: If the voltage is 12V and the resistance is 4Ω, then current I = 12 / 4 = 3A.

Use the formula: R = V / I. Example: If the voltage is 24V and the current is 6A, then resistance R = 24 / 6 = 4Ω.

- Voltage (V) is measured in volts (V).
- Current (I) is measured in amperes (A).
- Resistance (R) is measured in ohms (Ω).

Ohm’s Law applies to linear circuits where resistance remains constant. However, in cases like semiconductors or superconductors, resistance may vary, making Ohm’s Law less accurate.

Power (P) in an electrical circuit can be calculated using:P = V × I, or using Ohm's Law:P = I² × R or P = V² / R.

If resistance is zero, the circuit becomes a short circuit, causing infinite current flow, which can damage components or cause overheating.

Yes, but in AC circuits, impedance (Z) replaces resistance (R), considering inductance and capacitance. The modified formula is V = I × Z.

Ohm’s Law is used in designing electrical circuits, calculating the right resistor values for LEDs, determining wire sizes, and troubleshooting electrical issues.

Power (P) in an electrical circuit is the rate at which energy is transferred. It can be calculated using P = V × I, P = I² × R, or P = V² ÷ R, where V is voltage, I is current, and R is resistance.

Ohm's Law doesn't apply to non-ohmic devices where resistance varies with voltage or current, such as diodes, transistors, and other semiconductor devices. It's primarily applicable to conductors with constant resistance.

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