1. Voltage and Circuits: The Intro
Okay, see, it’s like this….

2. Remember Potential Energy?
Picture, if you will… q0
F = q0E H1
F = mg
F = q0E q0
F = mg H2
What are the two PE’s
of the basketball?
What is the work done?

3. Electric Potential Difference
In the previous slide, we saw that the work done = difference in electrical potential energy
If we divide the work done by the charge q0, we get the ELECTRIC POTENTIAL
This is also the VOLTAGE.
Electric Potential V at a given point is the electric potential energy of a small test charge q0 divided by the charge itself.
1 volt = 1 joule/coulomb

4. Volts 1 volt = 1 joule/coulomb
This means that 1 volt is the potential difference across which one coulomb of charge gains or loses 1 joule of energy

5. Just to annoy the students…
The following terms all mean the same thing:
Voltage
Potential Difference
Electrical potential
In this class, I will try to stick with ‘voltage’. But if you ever hear any of the other ones, that’s what they mean.

6. Electric Circuits
There are three main quantities we care about when we talk about electric circuits
Voltage
Current
Resistance
Let’s talk about these individually

7. Current
Current is the amount of charge flowing past a certain point in the circuit in a certain length of time.
Think about the water current in a river: how much water goes past a certain point in a certain time.