Divider Node Voltage - Electronic Circuits Step by Step

A voltage divider uses two resistor drops to make a node voltage. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

A divider is two resistors in series

The output node sits between the top resistor and the bottom resistor.

\text{output node is between the two drops}

Compute the series current

The source is 12 volts. The resistors are 2 ohm and 4 ohm, so the current is 2 amperes.

I = \frac{12\ \text{V}}{2\ \text{ohm} + 4\ \text{ohm}} = 2\ \text{A}

Compute the two drops

The top resistor drops 4 volts. The bottom resistor drops 8 volts, and that bottom drop is the output voltage.

V_{\text{out}} = V_{\text{bottom}} = 8\ \text{V}

The output is the bottom share

Keep the source at 12 volts. The output follows the fraction of total resistance below the output node. The diagram shows the middle row.

\begin{array}{c|c|c|c|c|c}V_{\text{in}}&R_t&R_b&I&V_t&V_{\text{out}}\\12\ \text{V}&1\ \text{ohm}&3\ \text{ohm}&3\ \text{A}&3\ \text{V}&9\ \text{V}\\12\ \text{V}&2\ \text{ohm}&4\ \text{ohm}&2\ \text{A}&4\ \text{V}&8\ \text{V}\\12\ \text{V}&3\ \text{ohm}&3\ \text{ohm}&2\ \text{A}&6\ \text{V}&6\ \text{V}\\\end{array}