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Power in Series and Parallel Circuits

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This is a demonstration of power in series and parallel circuits. We're going to use light bulbs and a regular AC socket. You can use the brightness of the bulbs as a measure of the power dissipated by the bulbs this is a little bit different than a normal AC socket. One one side we have two outlets that are white and on the other side we have two outlets that are brown. Let's see the difference between those. I have a 40 watt bulb here. It does what it should do when you plug it into a socket; it should come on and the other 40 watt bulb right there; alright so both of them are on. Nothing unusual about that.

Now I'm going to move the bulbs over to the other side. When I plug into the brown socket the bulb doesn't come on, when I plug into the other brown socket, both bulbs come on although they are dimmer than they were before; alright so what's the difference between the two? Well these two sockets are wired in parallel as you would normally wire AC sockets in the wall. But these others are wired differently for demonstration purposes. They are wired in series. And so, as you know from a series circuit since everything is one complete chain, if one component is removed everything goes out.

Let's look at the situation now for two bulbs of different power. This is our forty watt bulb, which means that when it's plugged into a socket it dissipates forty watts of power. This is a twenty watt bulb, I'll plug both of them in to the parallel side and this bulb dissipates twenty watts of power. Let me unplug this one so you can see wether or not this one changes brightness when I unplug the other one. Stayed about the same okay, and likewise when I unplug this one it doesn't have any noticeable effect on this one. Alright, let's plug the two bulbs in to the other side series side so the bulb doesn't come on until I plug in the other one. Stop and think for a moment about what you think will happen. The situation is quite a bit different here than it was before. Now the twenty watt bulb is much brighter than the forty watt bulb. For the forty watt bulb you can just barely see the filament glowing on it, so the forty watt bulb is not producing nearly as much power as it did when it was plugged into the parallel side. And the twenty watt bulb as you can tell is not producing as much power as it was when it was plugged into the parallel side. So, your job will be to do some circuit analysis on these situations and show that this result is actually the expected result.



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