Divider Ratio Direction Scan - Electronic Circuits Step by Step

A fixed source and fixed total resistance scan show how moving resistance between top and bottom changes the output 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

The output follows the lower share of the divider

The source voltage is fixed. The top and bottom resistors still carry one series current, but the output node reads only the bottom resistor's voltage share.

V_o = V_s\frac{R_b}{R_t+R_b}

Three resistor ratios show the output direction

Each row keeps the same source voltage and the same total resistance. Moving resistance from bottom to top moves the output down because the bottom share is smaller.

\begin{array}{c|c|c|c|c|c}V_s&R_t&R_b&I&V_t&V_o\\12\ \text{V}&1\ \text{ohm}&3\ \text{ohm}&3\ \text{A}&3\ \text{V}&9\ \text{V}\\12\ \text{V}&2\ \text{ohm}&2\ \text{ohm}&3\ \text{A}&6\ \text{V}&6\ \text{V}\\12\ \text{V}&3\ \text{ohm}&1\ \text{ohm}&3\ \text{A}&9\ \text{V}&3\ \text{V}\\\end{array}

The middle row splits the source exactly in half

For the rendered row, the current is 3 amperes. The top drop is 6 volts and the output drop is 6 volts.

6\ \text{V}+6\ \text{V}=12\ \text{V}

A ratio scan is stronger than one example

The scan shows the direction without changing the source or the total resistance. The diagram and table agree on which resistor owns the output share.

R_b\uparrow\Rightarrow V_o\uparrow,\quad R_t\uparrow\Rightarrow V_o\downarrow