Beginner Electronics

Beginner Electronics – 15 – Ohm’s Law

what is going on everyone my name is code Mort and welcome back to electronics episode 15 now before we get started in today's episode let's take a

look back into episode number 7 now in episode number 7 we were trying to find how much resistance we would need to protect our led inside of a circuit and we used this equation right here to

calculate that so we said that the resistance value in ohms the value of resistor that we would need to put in our circuit to protect the LED is equal to the source voltage or basically our

power source so for me I was using a 9 volt battery minus the forward voltage of our LED which can be found on your LEDs datasheet from whoever made your LED all divided by the current that we

wanted the LED to take up which could also be found on your manufacturers data sheet for your LED now this equation is actually a variation of one very very important equation in electronics work

this equation is going to be the most important thing that you ever take out of this series and that is called Ohm's law now the equation above that I just scrolled up is actually a variation of

Ohm's law now Ohm's law is actually this equation right here V equals I R voltage equals current times resistance now I'm going to explain to you why this is super

important but for right now let's take a look at this equation voltage equals current times resistance now if we did some very basic math that I hope that you guys should be able to do if we just

divide each side by R we can figure out that current equals voltage divided by resistance or if we took this equation and divided each side by I or by current we can figure out that our resistance

equals voltage divided by current so these are the three equations that we can get from Ohm's law so as long as we know two of these three variables as long as we know voltage and resistance

or current in resistance or some two variables we can find the third one using one of these equations so in our case to find out the proper value resistor we use this bottom equation R

equals V divided by I if we scroll up to the original equation we have R equals voltage this is all voltage here / I so let me exactly explain how this all worked and

why I got to that now Ohm's law is used to explain that we can solve for anything between two points now in our case the two points was the entire circuit basically the positive and

negative terminal of the battery in what we actually calculated was very simple you just got to think about it now for my led from my led of course this could be different my led could

take a maximum of three point two volts and it had I think 0.2 4 milliamps or something like that I don't think that was actually it but nonetheless my LED could take my maximum of 3 point 2 volts

and let's say 0.2 4 milliamps and we knew that my battery my battery was a 9-volt battery now a 9-volt battery is way too much voltage for this LED this LED would burn out and not work at 9

volts because it can only take a maximum of about 3 point 2 volts so all we did in that equation was say alright we need something in our circuit that will take away the extra voltage from the battery

so if we take our 9 volts minus the 3 point 2 volts the LED needs that gets us 5 point 8 volts so we needed something in our circuit that would waste or take away 5 point 8 volts that way the LED is

left with its maximum 3 point 2 volts so if we take a look at this a bit more closely we know two of the variables we know five point eight volts and we also know the current the maximum current we

want to run through our circuit which in the example here is 0.24 milliamps so we know current we know I we know voltage so if we know voltage and I we can solve for resistance and to

create resistance in our circuit we use of course a resistor so that will give us the value of resistor that we would need in our circuit so that's a bit more in depth of an explanation of kind of

what we did in episode number seven with this equation here but I don't want you to remember this equation here I want you guys to remember Ohm's law V equals IR and also I equals V over R or

equals the over I with this equation we can solve and test for so many things inside of our circuit now at first Ohm's law might be a bit tricky to understand you might have a bit of trouble

understanding what values to put into what and why we need to solve for stuff but throughout this series you're going to learn exactly how to use it properly and it's going to come as a natural

instinct later on but it's very important that you know this equation for the rest of the series and for any electronics work that you do I know these videos have been a bit boring so

far doing a lot of diagram stuff but I want to get this stuff out of the way before we do the actual exciting electronics work thanks for watching everyone and us you guys in the next

video

We talk a bit about Ohm’s Law and an important equation!

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