What is a DC circuit? DC stands for direct current circuit, which means that the circuit is connected to a source of power, in most cases, a battery.
This is an example of what a series circuit looks like. Both bulbs are equally as bright because the current, or flow of charge, through both is the same. In a series circuit, the total voltage is equal to the sum of the voltage drops that are in each light bulb/resistor. An ammeter can be used to measure the current in a circuit, but only if it connected in series. Also, the equivalent resistance is equal to the sum of the ohms in both resistors, and as a result, the equivalent resistance increases with each added resistor. The equivalent resistance is the amount of resistance that a single resistor would have if replaced both circuits. If one light bulb is removed, then every light in the circuit goes out, because it breaks the series.
Parallel Circuits
This is an example of a parallel circuit. Unlike in series circuits, the resistors in this circuit are not side by side, but parallel from each other. In this circuit, each bulb is differently lit because the current through each is not the same. The total current splits itself inbetween the three lightbulbs, as it is not one single path, giving each one their own current. However, the voltage drops in the resistors are equal in each bulb, so they are all individually equal to the total voltage. Also, unlike in the series circuit, with each resistor added, the equivalent resistor goes down. If one light is taken out, then the other one remains.
Complex Circuits
The last type of circuit shown is a complex circuit. This is what occurs when parallel circuits and series circuits are combined to make one whole circuit. The total resistance is found when the equivalent resistance for the parallel circuit is found and the equivalent resistance for the series circuit is found and the two quantities are combined. The reason that they are combined instead of finding the reciprocal of both and then finding the reciprocal of that, as in a parallel circuit, is because the series circuit and the parallel circuit are in series with each other, so the complex circuit acts a lot like a series circuit. The resistor that is in series with the rest is brightest because, since it is in series, the total current flows through it. Then it splits between the two resistors in parallel. To find the total current in the whole circuit, you just treat it like a regular circuit and divide the voltage drop by the total resistance. The voltage drop in the parallel part of the circuit is equal for both resistors, and then the series part gets the voltage drop that is left over from the total voltage. In this circuit, if you take the resistor/light bulb in series out, then all the light bulbs go out. But if you take one of the parallel circuit light bulbs out, then the other parallel circuit and the series resistor remain lit, and become a series circuit.
