Ok all, there are a bunch that don't know ohms law! Using Wikipedia to learn it doesn't work. I had to read about it and be taught. So i want to make a guide for those who don't know. Now this may be in the wrong section but seemed like the best place to me. Any how here we go......
Ohms law. It is used to help calculate voltage, current and resistance.
Lets start with Voltage.
Voltage which is substituted with a "V" when used in a formula. Voltage is measured in Volts. It is the amount of pressure the battery has. Often used with a water analogy. Voltage is like the pressure in your sink.
The formula to figure out voltage is V=IxR
You will learn that later.
Moving along we have Current.
Current is substituted with a "I" for formulas. It is measured in Amps. It is how much electricity is moving though the component. (not as vague as electricity but for simplicity's sake we will leave it at that for now.) Often used with the water analogy. Its the amount of water moving through the sink.
The formula to figure out current is I=V/R
Also learned later.
Now to Resistance.
Resistance is substituted with a "R" for formulas. It is measured in "Ohms". it is the Resistance on the Current. It also is used in the water analogy. It is like the length the pipes have to travel and how small they are, limiting how much can get through. As well as how open the valve is. ex. how open the valve on the handle is. Resistance in electronics can be how small the wire is, resisters (name says it all. it resists current. cause resistance= limiting HOW MUCH can come through and current is HOW MUCH) how long the wire is. the type of material Current is moving through.
Although not as effecting is the length of the wire. It is not hugely affected much, but it technically does limit some, not anything to worry about though. And if you have to small of a wire it will heat up and stop working in that circuit.
Recap: Voltage is the pressure, Current is how much and Resistance is limiting how much.
So if pressure pushes how much and how much is limited that means Voltage moves Current through while Resistance limits Current.
So now for the formulas.
V=IxR means that Voltage is equal to Current multiplied by resistance.
So understanding this now you realize to find one you must have two.
So let’s pick this apart. Its basic algebra. Replace the variables with the numbers. If you are trying to find Voltage then you need current and resistance values. So let’s say the resistance was 100 ohms. And the current was 0.12 amps. That would be 0.12 x 100 = 12 volts.
I=V/R means current is equal to voltage divided by Resistance. Again replace the variables. Let’s use the same equation. So as seen before if we have 12 Volts and 1oo ohms then respectively 12/100= 0.12 amps
R=V/I means resistance is equal to Voltage divided by current. Same equation again means that with 12 volts and 0.12 amps, the formula is 12/0.12 = 100. Hasn’t changed.
So you can see how a formula works with changing out variables with what you know.
ex.
V=IxR
V=0.12xR
V=0.12x100
V=12
Not to hard is it?
So how do you have two of these variables and still need another? Well let’s look at it as a problem. If you have a LED with a high voltage of 7 volts and 3 amps, but a battery with 7 volts and 5 amps then you need a resister. A resister resists the amount of current, which is what is too much. So now you need to find out the size of the resister you are using. So if you need 2 amps at 5 volts to be limited from your battery to your LED. so you use the formula R=V/I to find your resister size. so let’s do it!
R=V/I
R=5/I
R=5/2
R=2.5
There for you need a resister with 2.5 ohms. That will limit your 2 amps to your LED.
Now limiting voltage is different. It’s not done the same way. Resistance limits how much remember not the pressure. so what does limit voltage? Nothing really. Voltage is decently something you can have stray from specs. For instance i have a 12 volt battery but a 24 volt motor. It just pulls twice the current. Same as well the LED will only draw so much voltage. But at the same time you can’t overdue it. Now in a project I’m going to do I’m going to use this same 12 volt supply to power some LED's. Small ones mind you. And i will use what is called a voltage regulator for that.
a voltage regulator steps down the voltage. There is no equation for this. On the package the regulator will say how many amps and volts your power supply will be dropped to. Because that is not affected the way a resister and amps are. it takes the voltage incoming and drops it to what it is set to.
So if you have too many volts to a component you need then you need to either step down the power supply to a more appropriate voltage or use a regulator. Generally getting a battery with less voltage or using a smaller amount of batteries if you are using many.
Understanding resistance, current and voltage written.
Voltage which is volts may also rather than being written like 12 volts may be written like 12V. V standing for Volts.
Current which is amps may be seen as 0.12A rather than 0.12 Amps.
a tip to remembering the formula's that i found easy is this, if you can remember the three letters in the equations then its simple. Voltage always likes to be on top. when calculating voltage it is the only one that uses multipilication instead of division. when calculating current and resistance it is division. and voltage will always be on top. only one multiplication when voltage can not be on top.
Resistance which is ohms may just be seen as simply 100ohms.
So now you can read it when its written and you know what resistance, current, and ohms law is. You can also now calculate voltage, resistance and current. You are set to go! Now you can calculate your own circuits!
I may just do a tutorial on components and stuff to….. not sure yet.
Anyway if any other members want to chime in they can. Any criticism is appreciated! Sure I didn’t do perfectly.
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