1. Electrical Potential
Voltage

2. How can we manipulate energy in electric fields?
Apply FORCE to push like charges TOGETHER FA FA + +
Apply FORCE to push unlike charges APART FA FA + -

3. How much electrical PE?
Electrical P.E. is also called VOLTAGE or POTENTIAL DIFFERENCE
Unit = VOLT
1 Volt = 1 Joule/Coulomb

4. Example #1 V = W q V = 6 J 3C V = 2 J/C or 2 V
An object with +3 coulombs of charge is pushed toward a positively charged plate. 6 joules of energy are expended in pushing the charge. What amount of electrical potential energy has been stored in the field between the charged object and the plate?
V = W q
V = 6 J 3C
V = 2 J/C or 2 V

5. - - Removing Energy - - - - - - - - - - - Example #2
An object with 2 coulombs of charge
is accelerated using an electrical
potential of 10 volts. How much
kinetic energy does the object
receive?
Removing Energy
This stored energy can also be released.
What happens to energy that comes OUT of a field?
Transfers into kinetic energy
V = W q
10 V = W 2C
W = 20 J
The field releases
the energy, doing
WORK on the charge! - -
STORING ENERGY

6. Example #3
An object with a charge of 0.5 coulombs is pushed 0.2 meters toward a negatively charged plate with a force of 10 newtons.
What is the energy required to do this?
W = Fd = (10 N)(0.2 m) = 2 J
What is the electrical potential energy of the object after it is pushed?
V = W = 2 J = 4 V
q C

7. Example #4
An electron travels a distance of 2 x 10-3 m while being raised to an electrical potential of 3000 volts. What is the work done on the electron?
V = W / q
W = Vq = (3000 V)(1.6 x C) = 4.8 x J

8. Electron-volts 2 eV 4 eV 4 eV = 6.4 x 10-19 J 2 eV = 3.2 x 10-19 J
The electron-volt (eV) is a unit of ENERGY
Electron-volts are a SHORT CUT to finding
ENERGY when dealing with
FUNDAMENTAL CHARGES.
An electron-volt is the amount of energy
needed to raise the electrical potential of
an electron (or proton) by 1 volt
What is the energy
needed to raise two electrons to a potential of 1 volt?
What is the energy needed to
raise two electrons to a potential of 2 volts?
2 eV
4 eV
4 eV = 6.4 x J
2 eV = 3.2 x J

9. What use is electrical potential?
Higher VOLTAGE
We use this by putting a
RESISTOR in the path
of the ELECTRONS – as
they go through
the RESISTANCE they
do WORK on it!
The electrons naturally “want”
to drop to a lower energy
How do they get there?
A battery is a tool that forces
electrons to a higher
electrical P.E. - gives
them VOLTAGE
RESISTOR