Electric potential energy, like gravitational potential energy, increases as an object is moved against an electric field. Voltage, also called electric potential, measures the electric potential energy of a charge and the work required to move it between two points in an electric field. Voltage is defined as the work done per unit charge to move an object from one point to another in a constant electric field. A battery supplies voltage that provides electric potential energy to charges moving through a circuit.

2. Gravitational Electric
E
Electric vs. Gravitational
g Potential Potential
Energy Energy
Increases Increases
-
+
• Work is needed to • Work is needed to
push an object push a charge against
against gravity and a field and give it
give it Potential Electric Potential
Energy
Energy

3. Potential Difference
Potential Energy & Potential Difference
 Voltage (scalar or vector)
Divide both sides by qo What does voltage
and you get another actually measure?
physical quantity: – Measures how much
Electric Potential! energy a charge will
Otherwise known as gain/lose
voltage! – Measures how much
work that can be
done by a charge
If the Electric Field is
constant, it comes out of
the integral and you get
V = Ed

4. Allesandro Volta
Uniform Electric Fields
(Italian: 1745 – 1827)
Parallel Plates
Point
charge
Note the field lines
Uniform electric field

5. Battery gives the
electron 12 J of
Potential energy
e “loses” energy as it
travels through the
circuit.
Analogy
12 V
0V
Battery “gives” energy back
to electron to repeat cycle

7. • Sample Problem
Potential Energy & Potential Difference
A 9 V battery is connected to two parallel
plates that are separated by a distance of 0.30
cm.
a. What is the electric field?
b. How much energy would an electron have when placed
next to the positive plate?
+ + +
D = 0.04m
– – p+ –
a) V = E d b) Ue = q ∆V
9 = (E)(0.003m)
= (9 V)(1.6 x 10-19C)
Ue = 1.44 x 10-18 J
E = 3000 V/m

8. Key Ideas

9. times
charge
compliments of Mike Gearon
Flow Chart
times per unit = Potential
distance = Work
distance Gradient
per unit
charge

10. times
charge
compliments of Mike Gearon
Flow Chart
times per unit = Potential
distance = Work
distance Gradient
per unit
charge