Electric potential


  • To understand the definition of potential
  • To see the connection between work done and area under the F – x graph
  • Understand the relationship between line of equipotential and field lines.
  • Sketch lines of equipotential
  • Understand the relationship between V and PE
  • Define the eV

Observations and common pitfalls

It should be easy to memorise; "The work done per unit charge in taking a small positive test charge from infinity to the point in question." But students seem to find it difficult, they always miss out the per unit charge bit. Strange when they can memorise a long speech in a play. It's true that it's better to understand than memorise but at the end of the day they need to know the definition to be able to apply it.

This topic is a good example of the way knowledge in physics builds up, to be able to understand electrical potential the student needs to already understand (TOK):

  • work
  • force
  • Coulomb's law
  • force distance graphs

Having gained an understanding of potential it will be used in:

  • electric circuits
  • atomic and nuclear
  • photo electric effect
  • relativistic mechanics
  • electro magnetic induction

I often tell my students that when they hear the word potential it should have an instant meaning: The work done per unit charge in taking a small positive test charge from infinity to the point in question. At first they need to recite the meaning but after a while they won't need to. It's like the first time you are told what a horse is. Four legs a mane and a tail made of hair. At first time you see a horse you think does it have four legs a mane and a tail made of hair? Yes, it's a horse. After a while you just know it's a horse, the picture is built into your brain. (TOK)

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