Voltage drop and current?

Current doesn't change in a series circuit. It's all based on Ohm's Law: Current ("I", measured in "amps") = Voltage ("E", measured in volts) / Resistance ("R", measured in Ohms). Resistors in series add. Resistors in parallel divide as such: Rtotal = 1[(1/R1)+(1/R2)+(1/R3)...]. First, picture a 10 volt power supply, feeding three resistors in series, a 50 Ohm, a 30 Ohm, and a 20 Ohm. Do the math, based on Ohm's law. The total resistance is 100 Ohms, so the current throughout the circuit is a constant 100 mA (0.1 Amps). The 50 Ohm will have 5 volts dropped across it, the 30 Ohm will have 3 volts dropped across it, and the 20 Ohm will have 2 volts dropped across it. Now, put the same three resistors in parallel, and do the math. The total Resistance will be about 9.7 Ohms. All three resistors obviously have 10 volts dropped across them. The 50 Ohm will have 0.2 amps passing though it, the 30 Ohm will have 0.333 amps passing through it, and the 20 Ohm will have 0.5 amps passing through it. The total load on the power supply, about 1.033 amps is the same as the 10 volts divided by the total resistance of 9.7 Ohms. You can apply Watts Law, P (Power, in Watts) = I x E to see how much power is dissipated by each resistor. "Energy" is simply Watts times time, just like your light bill.

The biggest thing that helped me was the thought that each peace of wire that is directly connected has the same voltage. So if you split one wire (or connect an extra) so you can run each new end to a different light, those connected wires have the same voltage. Usually you also combine the wires coming out as you complete the circuit. These also have the same voltage but the light bulbs in the middle cause a voltage drop.

Now if you run them in a line the first light bulb has an in voltage then a voltage drop (from the bulb), the next bulb recieves this new voltage and causes another drop....

say that now you split this wire to connect two bulbs, they have the same in-voltage, and if you connect them on the other side you have the same out voltage, thus the same voltage drop. It finally understood it when I looked at a diagram an the TA drew each wire a different color.

For much more detail to go beyond this you need the equations.

Here's an article that explains it:

http://www.helium.com/tm/846245/field-electronics-...