'''What is potential difference?''' It's pretty simple, actually.
* A charge repels other like charges (with same sign). That means, an electron repels other electrons.
* If you at one point have, say, 10 electrons then they will try to move as far away from each other as they can.
* This point with many electrons (that is, this point that electrons are strongly repelled from) is said to have ''high potential''. A point of less repulsion is said to have ''lower potential''.
In this way, electrons will always try to move towards the lower potential. In other words: ''if there is a potential difference between two points'' then electrons '''will try to move''' because they experience an electric force ''towards the lower potential''.
'''How can such a potential difference be established?''' That's also pretty simple, actually.
To create and sustain a potential difference you need something to move charges "the ''wrong'' way". That is, towards the point of ''higher'' potential. You just need a force larger than the repelling force.
* a battery is a clear example. Inside the battery a chemical process creates such a force which pushes the electrons back up to the higher potential point (the negative pole/terminal of the battery).
* From this point they again want to move back to the lower potential. They do this by running through the circuit ("around" the battery).
* When the electrons reach the lower potential, which is the positive pole/terminal of the battery, they are moved back up again on the higher potential ready to travel once more
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