Potential divider Flashcards – AQA A-level Physics (7408)

What is a potential divider?

Resistors in series across a supply that provide an output potential difference equal to a fraction of the supply potential difference.

Why is the potential difference across each resistor in a series potential divider proportional to its resistance?

The same current flows through each resistor.

For a two-resistor potential divider, what is the output potential difference across $R_2$ when the output draws negligible current?

$V_{\text{out}} = V_{\text{in}}\frac{R_2}{R_1+R_2}$

With a constant supply, how does a potential divider’s output depend on its resistances?

Fixed resistances give a constant output; changing a resistance changes how the supply potential difference is divided and hence changes the output.

How can a sliding-contact variable resistor provide an adjustable potential divider output?

It selects a continuously variable fraction of the supply potential difference.

How can an NTC thermistor make a potential divider’s output depend on temperature?

Its resistance decreases as temperature rises, changing the output.

How can an LDR make a potential divider’s output depend on light intensity?

Its resistance decreases as light intensity increases, changing the output.

What determines whether a sensor potential divider’s output rises or falls as the sensor’s resistance changes?

Which component the output is taken across.