9702 · 10.3
Common exam mistakes on 9702 Potential dividers. Learn what loses marks, then practise the topic with Examiner’s Ink.
Always clearly identify which resistor the output voltage is being taken across in the potential divider formula; a common mistake is using the wrong resistance in the numerator. Also, understand how sensors (LDRs, thermistors) change their resistance based on external conditions, and how this affects the overall resistance ratio and thus the output voltage.
If you increase the resistance of the resistor across which the output is taken (R2 in the formula), the output voltage will increase, assuming the other resistor (R1) and input voltage remain constant. Conversely, decreasing R2 will decrease V_out.
No, a potential divider can only provide an output voltage that is a fraction of, or at most equal to, the input voltage. It cannot step up the voltage.
A fixed potential divider produces a constant output voltage determined by fixed resistor values. In contrast, one using a potentiometer allows for a continuously adjustable output voltage by mechanically varying the resistance ratio.