key terms

As we get deeper into electricity, we need to learn the important terminology to be able to discuss electrical stuff.
The BAD thing is that everyone has heard the terms, and almost NOBODY (including you, probably) knows what they mean.
Voltage, current, resistance, power.
All are technical terms that you must use correctly.
Current (I) we've talked about. Measured in Amps, it is the rate of flow of charge through a circuit.
Resistance (R) is the amount of resistance to flow. It can limit the amount of current, and also can cause the heating in things like filaments. Measured in ohms.
Voltage (V) is electric pressure. The greater the voltage, the greater the current.
The relationship between these variables is: I=V/R or V=IR

The key ingredient in voltage is the idea of DIFFERENCE. Nobody is afraid of Kansas. Even though it has an elevation (in the western side) as high as 4000 feet above sea level. The reason nobody is afraid, is that there isn't much elevation variation. Similarly with electricity. Only a DIFFERENCE in voltages really makes a difference. That's why we connect to the positive AND the negative. Just like (take a moment to let this sink in...) a waterfall needs to have a top AND a bottom. It won't work with just all the water at the top (hanging out in Kansas). It needs to have a bottom as well (a path to flow to).

Tomorrow, we'll start looking more into the concept of voltage, and learn some static electricity stuff.