1. Voltage
And you

2. Every charge has an electric field
Just like every mass has a gravitational field
When the fields of 2 masses interact there is a force of attraction (Fg)
When 2 electric fields interact, there is a electrostatic force! (Fele)

3. A small positive test charge (qo) would move from point A to B
* Fele = E qo
(parallel to F = ma)
q1 pt.A
q1 has more EPE than q2
I would need to do work to move q2 pt.B
the charge from pt. 2 to pt. 1

4. So if position 1 has more EPE than position 2
Then it has more
Voltage!!!
Volt = electric potential = J/C
(potential difference, electromotor force, EMF)
The gravity parallel is when I hold an object up higher in the air, it has more gravitational potential energy

5. SO VOLTAGE IS:
A measure of the difference in electric potential at 2 separate points (or terminals on a battery)
This electric potential is transformed into other forms of energy (kinetic, heat, light)
If charges flow then potential can equalize

6. Analogous to:
A lake located at a high elevation that is connected to a lake at a low elevation
There is the potential for water to flow because of the elevation difference.
In a similar fashion charges have the potential to flow when there is a voltage difference (for example from one terminal of a battery to the other terminal).

7. Battery example:
charges not equalized = Potential difference present therefore voltage present charges equalized = no potential difference = no voltage

8. What can be done with voltage
All electronic devices transform EPE into other forms of energy – through the movement of charges (light, heat, magnetic fields)

9. EX: Transatlantic cable – Morris code communications
When the war of 1812 treaty was signed in Europe, the fighting did not stop across the Atlantic for weeks – because there was no way to communicate
~ 1850 work began on first transatlantic cable
Use of voltage difference to transmit messages
Very heavy and thick – problems with breaking, sinking to bottom of ocean

10. Voltage and Electric Potential Energy are measureable only in terms of work – one point relative to another point (just like GPE at one height is relative to GPE at an arbitrary zero point)

11. Back to the Voltage Basics
A + chg. accelerates from region of high electric potential (voltage) to regions of low electric potential.
A – chg. Accelerates from regions of low voltage to high electric potential (voltage)

12. Voltage equation summary:
V = Joules/Coulomb
R = resistance (ohms)
I = current (amps)
= Ohm’s law is: V = IR
Show PHET battery simulation

13. Electrodynamics investigation introduction
Flow of charges = current (I)
= charge/time = Δq/Δt
1 coulomb/ 1 sec = Ampere (amps)
Resistance (R) = voltage/current = V/I
1 volt/ampere = Ohm (Ω)
That is to say, lg. V with small current = high resistance

14. DC = direct current (moves in same direction)
AC = alternating current (changes directions)

15. Lab activity here…

16. Resistance in wires In a wire: R = ρ (L/A)
ρ = resistivity of the material (Ω  meters)
L = length, A = cross sectional area

17. POST LAB
Battery voltage has no voltage oscillations = DC = direct current
In series has additive effect on voltage