Ohm's Law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points. The fundamental formula is V = I × R, where V is voltage, I is current, and R is resistance.

What do the symbols V, I, R, and P stand for?

V = Voltage (measured in Volts), I = Current (measured in Amperes or Amps), R = Resistance (measured in Ohms), and P = Power (measured in Watts).

How does the calculator find all four values from just two?

The calculator uses different variations of Ohm's Law and the power formula (P = V × I). For example, if you provide voltage and current, it calculates resistance using R = V / I and power using P = V × I. All other combinations are solved similarly using the twelve different formulas derived from these two basic laws.

Ohm's Law Calculator (Voltage, Current, Resistance, Power)

How Does This Work?

This calculator uses the two fundamental laws of electrical circuits: Ohm's Law and the Power Law. By knowing any two values, it can solve for the other two using various arrangements of these formulas.

Ohm's Law: This defines the relationship between voltage, current, and resistance. The core formula is V = I × R. From this, we can also derive I = V / R and R = V / I.
Power Law: This defines the relationship between power, voltage, and current. The core formula is P = V × I. From this, we can also derive P = I² × R and P = V² / R.
The Calculation: When you enter two values, the calculator automatically selects the correct formula to solve for the two unknown fields and displays the results instantly. For example, if you enter Voltage (V) and Resistance (R), it will calculate Current (I) as V/R and Power (P) as V²/R.

The Surprising History of Ohm's Law

Georg Ohm, a German physicist, first published his famous law in 1827 in his book *The Galvanic Circuit Investigated Mathematically*. However, his work was initially met with scorn and dismissal by the German scientific community. His colleagues found his experimental approach to physics to be unsophisticated and the idea that something as complex as electricity could be described by a simple equation was considered absurd.

Discouraged by the hostile reception, Ohm resigned from his teaching position and lived in poverty for years. It wasn't until the 1840s, when his work was independently verified and promoted by scientists in other countries, that he finally received recognition. In 1841, the Royal Society of London awarded him the Copley Medal, their highest honor. The law that was once mocked became one of the cornerstones of electrical engineering, and the "ohm" was eventually adopted as the standard unit of electrical resistance.

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Frequently Asked Questions (FAQ)

Why do the fields automatically calculate?

This calculator is designed for speed and convenience. As soon as you have entered two valid values, it automatically calculates and fills in the remaining two fields. There is no need to click a "calculate" button.

What happens if I enter more than two values?

If you enter a third or fourth value, the calculator will overwrite one of the previously calculated results. The calculation is always based on the last two fields you edited, ensuring the results are consistent with your most recent input.

What if I try to input impossible values (e.g., 0 Volts and 1 Amp)?

The calculator will return "Error" or "Infinity" if you enter a combination of values that is mathematically impossible according to Ohm's Law, such as dividing by zero. In this case, use the 'Reset' button to clear the fields and start again.