Electric potential
Potential energy per unit charge, V = U/q. For a point charge V = k q / r. The unit is the volt, one joule per coulomb.
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Analogy
Height on a hill: charges roll from high potential to low.
Example
V = k q / rV = 8.99e9 x 1e-9 / 0.1V = 89.9 V
In practice
A 1 nC charge makes a potential of about 90 V at 10 cm.
Practice
Flashcards
- What is one volt?One joule per coulomb.
Interview questions
- Compare electric field and electric potential, and show how they are related for parallel plates.
- Field is a vector, potential is a scalar
- E = V/d
- Field points from high to low potential
Questions people ask
What is the difference between potential and potential energy?
Potential energy belongs to a particular charge in a field, in joules. Potential is the energy per unit charge at a location, in volts. A location has one potential, but a 2 C charge there has twice the potential energy of a 1 C charge.
Can potential be zero where the field is not?
Yes. Field is the slope of potential, and potential is zero only where its value is zero. Midway between equal and opposite charges, V is zero because the contributions cancel, but the field is strong there. Likewise, field can be zero where V is not.