In what circumstance would a variable resistor be unaccepted to vary voltage?

I am quite confused about when to use variable resistors and when to use potential dividers instead for the a level physics course, as for GCSE I always used variable resistors, do I always need to draw variable resistors now whenever a question asks for a circuit with variable voltage / resistance?

Reply 1

sigmagrindset49

If you just need the voltage varying by some unspecified amount, a variable resistor will always work and is the go-to solution.

Reply 2

duiwhidwhdi

Original post by sigmagrindset49

If you just need the voltage varying by some unspecified amount, a variable resistor will always work and is the go-to solution.

I thought this aswell but my teacher marked me down for not using the potential divider circuit once when i did that.

Reply 3

Joinedup

Original post by duiwhidwhdi

I thought this aswell but my teacher marked me down for not using the potential divider circuit once when i did that.

These questions aren't supposed to be about memorising 'variable resistor bad / potentiometer good. it's about reasoning which is the most suitable for the setup described by the particular question.

The potentiometer is connected between a couple of points in the circuit and as you move the slider from one end of the track to the other you get a continuously variable voltage between those extremes on the slider contact.

Variable resistor just varies resistance - the PD across the VR will depend on what current is flowing in the VR