Explaination to potentiometers ?

[MoAli]

Hey Guys,
Im desperate for help on that topic. I have no idea how the device work so an explanation would be appreciated; if someone can give me a hint on solving the problems when there are two cells in a circuit with different emf and the question says that when the potentiometer is at distance x emf is zero and then starts moving the slide of the device and asks about changes. Thanks

 

[matteo137]

The potentiometer is a device which resistance depends on the position of a cursor. This means that they are variable resistors, where the resistance is proportional to a constant (in units of ohm/meter) times a distance.