Ohms Law Calculator

The Fundamental Law of Circuits: Ohm's Law Calculator

Ohm's Law is the most fundamental principle in all of electronics and electrical engineering. Discovered by German physicist Georg Simon Ohm, it describes the relationship between three key quantities in a circuit: voltage, current, and resistance. The law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points, and inversely proportional to the resistance between them. This simple yet powerful relationship is the bedrock upon which all circuit analysis is built.

This calculator is an interactive tool that brings Ohm's Law to life. It allows you to enter any two of the three variables—Voltage (V), Current (I), or Resistance (R)—and it will instantly calculate the third. This is an indispensable utility for electronics students learning circuit theory, hobbyists designing their first circuits, and engineers who need to make quick, everyday calculations. It removes the need for manual algebraic rearrangement, letting you focus on the design and troubleshooting of your circuit.

The Three Forms of Ohm's Law

Ohm's Law can be expressed in three equivalent ways, which are often visualized using the "Ohm's Law Triangle":

• To find Voltage (V): V = I × R
  (Voltage equals Current multiplied by Resistance)
• To find Current (I): I = V / R
  (Current equals Voltage divided by Resistance)
• To find Resistance (R): R = V / I
  (Resistance equals Voltage divided by Current)

The units used are Volts (V) for voltage, Amperes (A) for current, and Ohms (Ω) for resistance.

Practical Applications

• LED Resistors: When adding an LED to a circuit, you must include a current-limiting resistor to prevent the LED from burning out. Ohm's Law is used to calculate the exact resistance value needed based on the source voltage and the LED's specific voltage and current requirements.
• Circuit Design: Engineers use Ohm's Law constantly to determine the values of components needed to achieve desired voltages and currents throughout a circuit.
• Troubleshooting: Technicians can measure voltage and resistance in a circuit to deduce the current flow, helping to diagnose faults and short circuits.
• Power Calculation: Power (in Watts) can also be calculated using Ohm's Law. The formulas are P = V × I, P = I²R, and P = V²/R.