Ohm's Law and Equivalent Resistance

Ohm's law relates voltage, current and resistance:

$U=I\cdot R \qquad P=U\cdot I=\frac{U^2}{R}=I^2 R$

Enter any two of the quantities $U$, $I$, $R$ — the calculator finds the third and the power $P$.

The second mode computes the equivalent resistance of a circuit. In a series connection the resistances add up, and in a parallel one their reciprocals add up:

$R_s=\sum R_i \qquad \frac{1}{R_r}=\sum\frac{1}{R_i}$

The resistance of a parallel connection is always smaller than the smallest resistor.