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**potentiometer question**

hey there

i hate coming online to ask for help but i am well and truly stuck!

attached is an image containing 2 potential divider setups.

i have a few questions about them, and any help would be appreciated!

a) for the first setup, A, how could the 10k pot be split into 2 resistors to give a Vout of 3v? i am confused by the +-15v source. can i treat this as if the +15v is 30v and the -15 is 0v? making the 2 resistors 9k and 1k? if not, how else is it done; i can find absolutely no examples of potential diviers which aren't grounded?

b) how do i calculate the thevenin source impedance of the potentiometer set to give 3v? im familliar with thevenin's theorem but dont fully understand the question. as far as i understand, thevenins thereom is used to reduc circuits down to just a voltage source, a resistor and a load; here i'm unsure how this would be done.

c)finally, how do i calculate Vout for the setup B when the effective impedance of the multi meter measuring Vout is reduced to 3.3K? my initial thought was a simple voltage division equation but this came unstuck when i realised that R1 = 0, therefore that doesnt work. im out of ideas after that!

like i said, i'd really really appreciate some help on this!

many thanks

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