- \n
- Current:<\/strong> Electricity has work to do, and when the electrons are flowing around a circuit, that\u2019s current at work.<\/span><\/li>\n\n\n\n
- Circuit:<\/strong> If it\u2019s a closed, continuous path, then electricity will flow on it. Along this path, electricity can do a ton of amazing things, like power your smartphone, or send humans to space! <\/span><\/li>\n\n\n\n
- Resistance<\/a>:<\/strong> This is what electricity encounters when it flows along physical material, whether that\u2019s a copper wire or a plain old resistor. Resistance restricts the flow of electric current.<\/span><\/li>\n<\/ul>\n\n\n\n
Below you\u2019ll find an image of a simple circuit<\/a>, which includes a battery, a switch, and a light bulb.<\/p>\n\n\n
The season of series<\/h2>\n\n\n
Say you have a strand of lights, connected one after the other. If you viewed this in a circuit, it would look something like this:<\/span><\/p>\n\n\n\n
![\"Series](\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2024\/10\/ChristmasLights-02_2.jpg\")
(Image source<\/a>)<\/em><\/figcaption><\/figure>\n\n\n\n When we plug our strand of lights into an outlet, what will the current do? Let\u2019s follow the flow:<\/span><\/p>\n\n\n\n
- \n
- Powering it up: <\/strong>When we plug our holiday lights in, the current starts flowing from our wall outlet.<\/span><\/li>\n\n\n\n
- Flowing along:<\/strong> It then moves along the strand of copper wire and through our holiday light, making it shine brightly. <\/span><\/li>\n\n\n\n
- Coming home:<\/strong> When our current reaches the end of our strand of lights, it heads for the ground to get some rest, and so the cycle continues.<\/span><\/li>\n<\/ul>\n\n\n\n
It doesn\u2019t matter what kind of components you place in a series circuit, you could mix and match capacitors, resistors, LEDs, and a bunch of holiday lights together and the current would still flow the same, from one part to another.<\/span><\/p>\n\n\n\n
Now, this is where holiday lights tend to have their downfall. What happens if you yank out one of those bulbs in your strand of lights? If your lights are anything like ours, then all of them turned off! Why is this? Think about it, if the current is flowing from light to light, and you disrupt that connection, then you\u2019re cutting off the path on which the electricity is trying to flow. This is called an <\/span>open circuit<\/b>.<\/span><\/p>\n\n\n
Current and resistance in series<\/h2>\n\n\n
There is a fundamental law of the universe to remember for how current and resistance work in a series circuit:<\/span><\/p>\n\n\n\n
The more work (resistance) that a series circuit does, the more its current will decrease.<\/p><\/blockquote><\/figure>\n\n\n\n
Makes sense, right? As you add more resistance to a circuit, like some holiday<\/span> lights, or even a resistor, then the more work for your circuit has to do. Let\u2019s say you take the circuit we introduced at the beginning of this blog that had one light bulb. Now, what would happen if you added another light to this circuit? Will both bulbs shine as brightly? Nope. When you plug in that second bulb, both will get equally dim, because you have added more resistance to your circuit, which decreases the flow of current.<\/p>\n\n\n\n
But how do you go about figuring out how much resistance you have in a series circuit? You just add all of the different resistance values together. For example, in the circuit below we have two resistors, each being 10k Ohms. To get the total resistance in this circuit, just add all of the numbers together. That\u2019s 10k + 10k, which comes to 20k Ohms of total resistance.<\/span><\/p>\n\n\n\n
And what would your current be in this circuit based on that amount of resistance? Here\u2019s how you can figure it out.<\/span><\/p>\n\n\n\n
- \n
- Using our trusty Ohm\u2019s Law Triangle<\/a>, we get the equation we need to use: I = V\/R, or Current = Voltage divided by Resistance.<\/span><\/span><\/li>\n\n\n\n
- Plugging in the numbers that we know, we get I = 10V\/20k. 0.5 milliamps (mA) are flowing through our circuit!<\/span><\/li>\n\n\n\n
- What if we took out one of the resistors? Now our equation is I = 10V\/10k, and we\u2019ve increased our current to 1 milliamp (mA) by reducing our resistance.<\/span><\/li>\n<\/ul>\n\n\n
Working in parallel<\/h2>\n\n\n
Now, wouldn\u2019t it be great if you pulled out one of the bulbs in your strand of holiday lights but the rest of them stayed on? If your holiday lights were all wired in parallel, then this is exactly how they would behave!<\/span><\/p>\n\n\n\n
In a parallel circuit, imagine your strand of lights all connected together. But instead of each bulb being connected one after the other, they are all connected separately, in their circuits like in the image below. As you can see, each bulb has its own mini circuit that is separate from the other, but they all work together as part of a larger circuit.<\/span><\/p>\n\n\n\n
![\"Series-parallel](\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2024\/10\/ChristmasLights-03_0.jpg\")
(Image source<\/a>)<\/em><\/figcaption><\/figure>\n\n\n\n But how does the current flow in this kind of circuit? It doesn\u2019t just follow one path; it follows all of them, all at the same time! Here\u2019s why this is awesome. Imagine that you yank out one of the bulbs in this type of circuit. Rather than stopping your whole holiday light operation, the rest of the circuit will keep on flowing because each light is not dependent on the light before or after it for its source of electricity.<\/span><\/p>\n\n\n
Current and resistance in parallel<\/h2>\n\n\n
When a circuit is wired in parallel, current and resistance start to do some strange stuff that you might not expect, here\u2019s what you\u2019ll want to remember:<\/span><\/p>\n\n\n\n
In parallel circuits, as you increase the resistance, you\u2019ll also increase the current, but your resistance gets cut in half as a result. <\/p><\/blockquote><\/figure>\n\n\n\n
Wait, what? That sounds crazy! But think about it regarding your holiday<\/span> lights. As you add more colorful lights to your circuit, then you need to draw more current to power all of those lights, right? And so a magical thing begins to happen, the more lights that you add, the higher your current climbs, but that increased current has an opposite effect on your resistance.<\/p>\n\n\n\n
This might be a bit tough to wrap your mind around, so let\u2019s go through a simple example. Say we have a 10V battery source and two 10k resistors that are connected in parallel. Now, since each resistor has its own circuit, we need to figure out how much current each will use:<\/span><\/p>\n\n\n\n
- \n
- Going back to our Ohm\u2019s Law Triangle, we know the equation we need to use is I = V\/R, or Current equals Voltage divided by Resistance. <\/span><\/li>\n\n\n\n
- And plugging our numbers in, we get I = 10V\/10k, which comes to 1mA. But that\u2019s only one of the two resistor circuits; we now need to double the current to get our total for the entire circuit, which is 2mA.<\/span><\/li>\n\n\n\n
- Now, what happens to our resistance at two amps? We can use Ohm\u2019s Law to figure it out with R = V\/I, which comes to R = 10V\/2mA = 5k Ohms. Because we doubled our current, our original 10k resistors are now only doing half the resistance!<\/span><\/li>\n\n\n\n
- <\/li>\n<\/ul>\n\n\n
How your holiday<\/span> lights really work<\/h2>\n\n\n
- And plugging our numbers in, we get I = 10V\/10k, which comes to 1mA. But that\u2019s only one of the two resistor circuits; we now need to double the current to get our total for the entire circuit, which is 2mA.<\/span><\/li>\n\n\n\n
- Plugging in the numbers that we know, we get I = 10V\/20k. 0.5 milliamps (mA) are flowing through our circuit!<\/span><\/li>\n\n\n\n
- Flowing along:<\/strong> It then moves along the strand of copper wire and through our holiday light, making it shine brightly. <\/span><\/li>\n\n\n\n
- Circuit:<\/strong> If it\u2019s a closed, continuous path, then electricity will flow on it. Along this path, electricity can do a ton of amazing things, like power your smartphone, or send humans to space! <\/span><\/li>\n\n\n\n
![\"Shunt](\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2024\/10\/ChristmasLights-04_1.jpg\")