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Potential
Physics 106
Units
Concepts
1.
2.
3.
4.
5.
6.
Electric Potential Difference, V
Electric Potential Energy, PE
Electric Potential of a Point Charge
Potential Energy of a Point Charge
Electron Volt, eV
Equipotential Surfaces
V Potential, Volts, (V)
PE Potential Energy, Joules, (N*m)
Nm 2
k e Coulomb Constant,
C2
q ..Individual Charge, Coulombs,(C)
E . Electric Field, (N/C)
d Distance, meters, (m)
e Charge of electron, 1.6E-19 C
Equations
q
V  ke :
r
V is called electric potential, or just “the potential”. It is different from electric
potential energy, which is:
qq
8.99  10 9 Nm 2
PE  k e 1 2 where k e 
r
C2
The key is the word “energy” at the end.
PE
V  VB  V A 
  Ed
q
Strictly speaking, all potential is a “change in” concept. Potential is a relative concept
that only has meaning when measured from some arbitrary zero point; like elevation,
which is measured relative to sea level.
Sample
Problem:
Find the electric potential, taking
zero at infinity, at the upper-right
hand corner.
Sample
Problem:
Suppose an electron is released from rest in a uniform electric field
whose strength is 5.90  10 3 V / m , Through what potential difference
will it have passed after moving 1.0 cm?
Physics Hero
Calculate the electric potential at
the midpoint of the base, given
q = 7.0 nC.
QQ6
QQ7
Sample
Exam
Problem
Two point charges of values +3.4 and +6.6 C are separated by 0.10 m. What is
the electrical potential at the point midway between the two point charges?
a. +1.8  106 V
b. 0.90  106 V
c. +0.90  106 V
d. +3.6  106 V
Don’t worry about: Work required to move a charge.