1. IV . Electric ______________
Potential
Move some _______________ from point A to B in
the E ( ________________ ) field of a charged object:
charge q
electric
E field ________
lines A q
charged
object F B
 It takes ____________ to move q closer because it
requires a ____________ applied for a ______________ .
work W
force F
distance d

2. Because of the work done, the energy of the
___________of charges is stored up as an electric _______ .
system PE
The electric _______________________ V is defined
as the work done per charge:
potential difference
V =
W / q
scalar
no direction
V is a _____________ because it has ___________________
units of V:
By definition,
one _______________________ = 1 _________
or _______ = 1 _____
[V] = [ ] / [ ] W q
[V] = / J C
joule/coulomb
volt
J/C V
 Because of its units, the potential difference is often
called the ________________ .
voltage

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4. Ex 1: 18 J of work are required to move 2.0 C of charge
between two points in an electric field. Find the electric
potential difference between the two points.
Given:
18 J = W
V = W / q
V = 18 J /2.0 C
= 9.0 J/C
= 9.0 V
2.0 C = q
V = ?
How much work would be required to move 4.0 C
of charge between the same two points of the problem
above?
V = W / q =
q =
4.0 C
V =
9.0 V
9.0 V
W/ 4.0 C
W = ?
36 J W
How much potential energy is stored up as a result?
36 J

5. DC volts in different sizes and shapes:

6. AC volts in different sizes and shapes:

7. NOTE: V = W/q can be used with 2 sets of units!
When working with small amounts of charge and energy, you often use _______________ units.
For W, instead of joules, use units:
______________________
For q, instead of coulombs, use units:
the number of ______________________
Using these new units, the potential difference V in:
V = W/q will have units: [ V ] = [ ] / [ ]
which again be volts: = /
You get V because _________________ .
smaller
electronvolts, eV
elementary charges, e q W V eV e
the e's cancel

8. Ex: 20 electronvolts of work are required to move 8
electrons between two points in an electric field. Find
the electric potential difference between the two points
V = W / q
= 20 eV / 8 e
= 2.5 eV/e
= 2.5 V
Given:
20 eV = W
8 e = q
V = ?
Ex: How much work (in eV) is done on a proton when
it is accelerated through a potential difference of
68,000 volts?
V = W / q
= /
68,000 V W
1 e
 W =
68,000 eV
How much kinetic energy will the proton have as a
result?
DKE = W =
68,000 eV

9. Conversions between units. See PhysRT, page ____:
1 electronvolt (eV) = _____________________ J
Notice that this number is the same as the one
in the conversion:
1 elementary charge (e) = _____________________ C 1
Ex. Convert 9.6 x J to eV.
9.6 x J x ___________________ = ______________ eV
Ex. Convert eV to J.
4640 eV x ___________________ = ___________________ J

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11. Conversions between units. See PhysRT, page ____:
1 electronvolt (eV) = _____________________ J
Notice that this number is the same as the one
in the conversion:
1 elementary charge (e) = _____________________ C 1
1.60 x 10-19
1.60 x 10-19
Ex. Convert 9.6 x J to eV.
1 eV
1.60 x J
6.0
9.6 x J x ___________________ = ______________ eV
Ex. Convert eV to J.
1.60 x J
1 eV
7.42 x 10-16
4640 eV x ___________________ = ___________________ J

12. Summary of electric potential units:
quantity
big units
small units W
(or energy) q V J eV e C V V
 eV's are NOT a unit of __________________________ .
They are a unit for __________ or _____________.
Also, you cannot mix: _____ with _______
or: _____ with _______
One of them must be converted first!
potential difference
energy
work J e C eV

13. Ex. Find the work done in joules in moving 5 electrons
through a potential difference of 6.0 V.
Solution 1: Find answer in eV, then convert:
V = W /q =
= W
________ eV x _______________ = ____________ J
Solution 2: Convert e to C first, then calculate.
_______ e x __________________ = ____________ C
6.0 V
W /
5 e
30 eV
1.60 x J
1 eV 30
4.8 x 10-18
1.60 x C
1 e
8.0 x 10-19 5
6.0 V
8.0 x C
W /
4.8 x J

14. NOTES:
Electric potential difference represents the ___________
per ____________ stored up in the system of charges. PE
charge
If the charges are allowed to move freely through a
potential difference, they will gain the energy as _____
in the same way that a ___________ object gains it. KE
falling
gravity:
electricity:
PE = 100 J
KE = 100 J
PE = 100 J
KE = 100 J