Ohm’s Law Calculator
Ohm’s Law Calculator
Instantly Calculate Voltage, Current, or Resistance
Enter Any Two Values
What is an Ohm's Law Calculator?
An Ohm's Law Calculator solves for voltage, current, or resistance in an electrical circuit when any two of the three values are known. It's a fundamental tool for students, electricians, and hobbyists working with basic electrical circuits.
How to Use the Ohm's Law Calculator
- Enter the two known values.
- Select which value you want to calculate: Voltage (V), Current (I), or Resistance (R).
- Click "Calculate" to instantly get the missing value.
Formula Behind the Calculation
Ohm's Law states:
V = I × R
Where V is voltage (volts), I is current (amps), and R is resistance (ohms). Rearranged forms give: I = V ÷ R, and R = V ÷ I, depending on which value you need to solve for.
Worked Example
If a circuit has a voltage of 12V and resistance of 4Ω, current is calculated as: I = 12 ÷ 4 = 3 amps. If instead you know the current is 3A and resistance is 4Ω, voltage would be: V = 3 × 4 = 12V.
Why This Tool Is Fundamental
Ohm's Law is the foundation of all basic circuit analysis, used constantly in electronics education, circuit troubleshooting, component selection (like resistor values for LEDs), and general electrical safety calculations.
Frequently Asked Questions
1. What are the three basic quantities in Ohm's Law?
Voltage (measured in volts), current (measured in amps), and resistance (measured in ohms) are the three interconnected quantities in Ohm's Law.
2. Can Ohm's Law be used for AC circuits too?
Yes, though for AC circuits with reactive components (capacitors/inductors), impedance replaces simple resistance in the more general form of the law.
3. Why is Ohm's Law important for choosing resistor values?
It helps calculate the exact resistor value needed to limit current to a safe level for components like LEDs, protecting them from damage due to excess current.
4. Does Ohm's Law apply to all electrical components?
It applies accurately to purely resistive ("ohmic") components; non-linear components like diodes and transistors don't follow a simple linear V=IR relationship.
5. How is power related to Ohm's Law?
Power (in watts) can be calculated using P = V × I, or combined with Ohm's Law as P = I²R or P = V²/R, depending on which values are known.