Important info:

Quiz Friday. It will cover basic circuits, light bulbs, electric current, and circuit diagrams.

Current homework due Friday.

Energy Audit due Oct 27.

• You need to look at your household energy bill
• you need to look at your electric meter
• you need to record your energy usage for a 24 hour period.
• you may need to borrow one of the watt meters to measure your usage.
• I only have three of these, and there are 50 students. So start early, share nicely.
• No whining about the meter not being available on the last day!!!
  

Electric current:
So, wires are made of metal. Metal wire has bazillions of electrons in it already. If you try to put in just a few more on one end, then some pop out the other end. The voltage source (battery) is the pusher. Since the wires are already "full" of electrons, the "pulse", or "domino effect" is what is important. Almost at the speed of light, the signal travels across the wire, so the light turns on instantly. The electrons that are moving through the wire, actually travel slowly.

Since there are bazillions of electrons (like 10^18 or 1000000000000000000 electrons) moving through the wire each second in a standard lightbulb circuit. That's a lot.

So, Mr. Coulomb said: let's just take 10^18-ish electrons and call that "one Coulomb". Then we can talk about coulombs per second of electric current traveling through the wires.

Mr. Ampere said: "OK, we can call 1 Coulomb/sec an AMP". :-)

And thus, electric current is measured in Amps.

Circuit diagrams:

This is not a *Drawing* but rather a diagram. You've been looking at them for more than a week now in our lab write-ups. I have been going increasingly away from "pictoral" representations and towards schematic diagrams. The menu in croc physics that you used for your first Vlab is pictoral. Next to that menu is the schematic menu.

Here's a helpful link to become familiar with diagrams of electric circuits.

http://www.kpsec.freeuk.com/cdiags.htm