Enter any two values to calculate the other two. Uses V = IR and P = IV.
Ohm's Law states that the voltage across a conductor is directly proportional to the current flowing through it, with resistance being the constant of proportionality: V = I × R.
The four electrical quantities (V, I, R, P) are related by two equations. With any two known values, the other two can be uniquely determined. Entering only one value leaves the system underdetermined.
Ohm's Law applies to ohmic (linear) conductors where resistance is constant. Non-ohmic components like diodes and transistors have variable resistance and do not obey this simple relationship.
The VIR triangle is a memory aid: cover the quantity you want to find - the remaining two show whether to multiply or divide. Cover V: I × R. Cover I: V / R. Cover R: V / I.