I've included diagrams where necessary to help you along. So, when you are ready, let us begin...
Math in electronics need not be boring. I discovered that when things were explained to me it become easy and fun too! I'll try to explain the basics without any fancy jargon and in the way that made it easy for me to understand. Hope you enjoy...
If you're like me you'll soon bore of endless pages of text and meaningless
formula's. It's inevitable you'll meet some of this but these will only be shown
when they are absolutely relevant. I use no fancy tools apart from a common
calculator - in fact you already have this at your fingertips... it's the calculator
which is included with Windows.
I've included diagrams where necessary to help you along. So, when you are ready,
let us begin...
The above formula is the basis of all measurements in electronics - and the easiest to remember! So what does it mean? Well, put simply, it enables us to calculate the unknown value of any variable (V, I, or R) when we know the value of at least two other variables.
Follow? No? OK, let's look at it an easier way...
Suppose we have a 9v battery and a 1000 ohm (1k) resistor. ('k' = kilo; kilo = thousand). Already we have two variables:- V and R. Now, what about the third, the "I"? In electronics, the I is used to express current. (This is measured in Amps so the I is just another way of expressing Amps, right?)
So, if we place the 1K resistor across the terminals of the 9v battery, a current will flow through the resistor. Now, before we go any further, I'd better explain that current is always measured through a resistor. Conversely, voltage is measured across a resistor.
OK, back to that I variable... We have 9v and 1000 ohms so a circuit has been made and current is now flowing.
So just how much current is flowing and how do we measure it? The answer
is quite easy when we apply some simple math. Refering to the formula at the top
of the page, it's easy to calculate. Place a thumb over the unknown variable (in
this case, the I) and read what you see. Only the V and R variables are left and
they are telling us therefore that the I must equate to the volts divided by the
resistance. ie: I = V divided by R. (I = V / R).
Load up your Windows calculator and enter '9' then click the "/" divide key. Press 1000 followed by the "=" equals key. Your answer will be 0.009Amps (9milliAmps or 9mA). Easy!
Using the same principle we can also find the unknown resistance if we
have the other two variables, V and I...
Place a thumb again over the unknown variable (this time it's R) and read what you see. In this case only the V and I remain so now we see that R = V divided by I. Using your Windows calculator again enter '9' then click the '/' divide key. Press 0.009 (9mA) followed by the '=' equals key. The answer this time is now 1000 (1k). This is too easy!
The last variable V is slightly different in as much this time we multiply
rather than divide. Place a thumb over the V and read what you see. Now we have
remaining I and R. This time you'll see that V = I multipled by R.
Run your calculator again and enter .009 then click the '*' multiply key. Enter 1000 followed by the '=' equals key. Our answer will now show us that I * R = ...9volts!!! Is this not just too easy?!
If you have a multimeter now is the time to put this to the test. After all, practice is a whole lot better than theory!
This formula has the same principles as the previous example. The only difference being that this will calculate Watts, Amps and Volts. It works the same so you should have no trouble. Once you know one formula it follows that you will know both. From these two formula's we can find any unknown variable by applying basic math. But there are drawbacks...
Suppose, for instance, we need to know quickly the total amount of Watts being used in a circuit. This is quite straight forward when we already know the voltage and current variables, but what happens when we don't?
First we need to divide volts by resistance to ascertain the current used. Then we multiply volts by current to arrive at the amount of power (W) used. A bit long-winded but there is an easier way...
Simply multiply I by I then multiply this by R... Presto - the result is W!
So, to recap on what we've learnt here, let's finish with a reminder...
V = I * R
I = V / R
R = V / I
For completeness, I've drawn this table to show how each variable can be easily found. It's simple to use and will quickly show the value of any unknown variable. Simply read any one of the formula's shown in blue and associate this to its equation shown in the red quadrant.
For example, V divided by I equals R - or if you prefer... R equals V divided by I
