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Basic Circuits

Real World Series Circuits

Switch series circuitOne simple application for this type of circuit would be a switch (Diagram to right). Lets say that device one is a wall switch, and device two is a lamp. If we turn off the switch, no current can flow. Because device two must have the same current as device 1, stopping the current in the switch stops the current in our lamp and it turns off. Device 3 might not be present(there is no requirement for a certain number of devices), or it could be another switch, a current meter, etc.

Another common application for series circuits is flashlights. In that case, we have batteries as our devices. While this may seam a bit strange, as the batteries are the power source, it still works the same way. We would have our load(the flashlight bulb) in place of the source. The voltage on our bulb is the total of the voltages of each battery added together. The current thru our bulb, and from each of the batteries, will all be the same amount.

You might wonder at this point what happens if one of the batteries is not as new as the others; it might seam that it wouldn't put out as much current as the other two newer batteries. The fact is, though, that the current will remain the same - only the voltage would be lower on that battery.

In fact, that's the reason you should always replace batteries in sets. If our weaker battery's voltage becomes low enough; it will actually become negative (reversed polarity). This will in effect cause it to start charging but in a reverse polarity. Depending on battery type, that can result in destroying the battery, leakage/bursting, or simply wasting some of the power from the other batteries.

One final point to remember about series circuits: a break or bad connection anywhere in the circuit will affect the entire circuit. Remember, the current must be equal everywhere. If we stop the current(make it 0 amps) with a broken wire between device one and device two, the current thru each of the other devices will also become 0 - meaning nothing will work. A well known example of this phenomenon is the famously unreliable holiday light strings. With 50 bulbs in a string (series circuit), that's a lot of chances for a bad connection!

Next, we will discuss parallel circuits.

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