Potential dividers

Was going through the specification and a few points I didn't really get.

"Explain how a potential divider circuit can used to produce a variable p.d"

So a potential divider is something that splits up the voltage. I am not entirely sure how you get a variable p.d. Does one of the components in the circuit have to change resistance so it would get a greater share of the voltage which would cause the p.d to vary. I guess you could use a thermistor an LDR or a variable resistor.

Can someone clarify what it means by that.

Another query similar to this is. "Describe and explain the use of thermistors and LDR's in potential divider circuits"

Can you add these into the potential divider circuit which would cause the p.d to vary. This would be because of the light level or the temperature?

Thanks for the help

You have pretty much nailed it already in everything you said.

A potentiometer is a variable potential divider which allows the ratio of the two resistances to be changed at will.

It's simply a piece of resistive material formed into a track and connected to an e.m.f at both ends, with a third 'wiper' picking off the p.d. as it slides up and down the track.



Which is the same as (120 ohm potentiometer example):

Ah got it! One thing though why would you put an LDR or thermistor in a potential divider circuit? Like is there a certain use of using these to alter the p.d?

Q's:

How would a variable p.d. be generated and measured if the LDR or thermistor were not placed in a potential divider circuit?

How would you (reliably) limit the current through the LDR or thermistor to prevent dissipating too much power within the device and thus thermally altering their I-V characteristics?