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Physics Calculator

Ohm's Law Calculator

Solve for Voltage, Current, Resistance, or Power by entering any two known electrical values.

Enter Any Two Values

Calculated Results

Voltage12 V
Current2 A
Resistance0 Ω
Power0 W

Reference Formulas

V = I × R
P = V × I
P = I² × R
P = V² / R
Physics Laws

Understanding
Ohm's Law

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

Four Variables

Connects Voltage, Current, Resistance, and Power. Inputting any two parameters solves the remaining two automatically.

Linear Proportions

Voltage is directly proportional to current. Doubling the voltage across a constant resistor doubles the current.

Safety Limits

Helps size circuit breakers and fuses. Knowing the resistance of a device helps prevent current overloads.

The Core Formula

The mathematical equation that describes this relationship is:

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

Where:

  • V (Voltage): Electrical potential difference, measured in Volts (V).
  • I (Current): Flow of electrical charge, measured in Amperes (A).
  • R (Resistance): Opposition to current flow, measured in Ohms (Ω).
  • P (Power): Rate at which electrical energy is consumed or generated, measured in Watts (W) and calculated as V * I.

Electrical Safety Tips:

  • • Oversize Wiring: Ensure wires are thick enough for the load current to prevent heat buildup.
  • • Fuse Ratings: Fuses should blow before wire insulation melts due to excess current.
  • • Grounding: Always provide a safe low-resistance path to ground for safety.

How the calculation works

Ohm's law relates voltage, current, and resistance. Power is voltage times current.

V = I × R P = V × I

Current is in amps, resistance in ohms, voltage in volts, and power in watts.

Worked example: 2 amps through 6 ohms

  1. Voltage = 2 × 6 = 12 volts.
  2. Power = 12 × 2 = 24 watts.
  3. Resistance = 12 ÷ 2 = 6 ohms.

A 12-volt circuit

CurrentResistancePower
1 A12 Ω12 W
2 A6 Ω24 W
3 A4 Ω36 W

Frequently asked questions

What voltage pushes 2 amps through 6 ohms?▼
12 volts.
What power is that?▼
24 watts.
How do you find resistance from voltage and current?▼
Divide voltage by current.