Download Potential Difference

Physics Section 17.1
Apply Potential Difference to Moving Charges
An object in a gravitational field has
potential energy if it is above the
ground.
The ball at point A has more potential
energy than the ball at point B.
A charged particle in an electric
field has more potential energy if
it is “above” the “ground”.
The particle has more potential
energy at point A than it does at
point B.
In the diagram, there exists
a difference in potential
energy from point A to
point B. This is referred to
as an electric potential
difference.
Electric Potential Energy in a Uniform Electric Field
PEelectric = -qEd
PE = electric potential energy (J)
q = charge on particle (C)
E = electric field strength (N/C)
d = displacement in a direction
parallel to the field (m)
Formula for Electric Potential Difference
Potential Difference is the work required to move a charge
between two points in an electric field divided by the
charge.
V=W
q
or V = PEelectric
q
V = potential difference (volt)
PE = electric potential energy (J)
q = charge (C)
A potential difference of one volt is the ratio of one
Joule to one Coulomb. (As a one Coulomb charge
moves through a potential difference of one volt, the
charge gains one joule of energy.)
Alternate formulas
Potential Difference in a Uniform Electric Field
V = -Ed
V = potential difference (V)
E = electric field strength (N/C)
d = displacement between two points (m)
Potential Difference in an Electric Field Generated by a Point Charge.
V = Kc q
r
V = potential difference (V)
q = charge (C)
r = displacement (m)
Kc = 8.99 x 109 N m2/C2
problems
1. A charge of 1.5 x 10-16 C moves 3.2
m in an electric field whose
strength is 250 N/C. Find the
change in its electric potential
energy.
2. A particle with a charge of 6.4 x
10-15 C gains 4.8 x 10-14 J of
electric potential energy as it
moves between two points in an
electric field. What is the
potential difference between the
two points?
problems
3. A particle moves a distance of 5.0
cm in an electric field whose
strength is 85 N/C. Find the
potential difference between the
particles initial and final position.
4. A particle with a charge of 8.2 x
10-12 C creates an electric field.
Find the potential difference
between two points that are 12
cm apart.
Assignment
• Page 601
• Problems 2, 4-9