INTRODUCTION TO BASIC ELECTRONICS

Definition of Electronics:   
 Electronics  is the branch of science that deals with the study of flow and control of electrons (electricity) and the study of their behavior and effects in vacuums, gases, and semiconductors, and with devices using such electrons. This control of electrons is accomplished by devices that resist, carry, select, steer, switch, store, manipulate, and exploit the electron.

Electronics isn't always easy, but you can learn. And you can do it without memorizing theories and formulas belong in a Physics text. the focus of this program is learning how things work. Electronics may defined as an art of knowledge to make such impossible things work. Things such as Televisions, AM/FM Radios, Computers and ob course the mobile phones and etc. We are  surrounded by electronics....What is Ohm's Law?

Ohm's Law is made from 3 mathematical equations that shows the relationship between electric voltage, current and resistance.

What is voltage? An anology would be a huge water tank filled with thousands of gallons of water high on a hill.
The difference between the pressure of water in the tank and the water that comes out of a pipe connected at the bottom leading to a faucet is determined by the size of the pipe and the size of the outlet of the faucet. This difference of pressure between the two can be thought of as potential Voltage.

What is current? An analogy would be the amount of flow determined by the pressure (voltage) of the water thru the pipes leading to a faucet. The term current refers to the quantity, volume or intensity of electrical flow, as opposed to voltage, which refers to the force or "pressure" causing the current flow.

What is resistance? An analogy would be the size of the water pipes and the size of the faucet. The larger the pipe and the faucet (less resistance), the more water that comes out! The smaller the pipe and faucet, (more resistance), the less water that comes out! This can be thought of as resistance to the flow of the water current.
All three of these: voltage, current and resistance directly interact in Ohm's law.
Change any two of them and you effect the third.

Info: Ohm's Law was named after Bavarian mathematician and physicist Georg Ohm.

Ohm's Law can be stated as mathematical equations, all derived from the
same principle.
In the following equations,
V is voltage measured in volts (the size of the water tank),

I is current measured in amperes (related to the pressure (Voltage) of water thru the pipes and faucet) and

R is resistance measured in ohms as related to the size of the pipes and faucet:

V = I x R (Voltage = Current multiplied by Resistance)

R = V / I (Resistance = Voltage divided by Current)

I = V / R (Current = Voltage Divided by Resistance)

Knowing any two of the values of a circuit, one can determine (calculate) the third, using Ohm's Law.

For example, to find the Voltage in a circuit:

If the circuit has a current of 2 amperes, and a resistance of 1 ohm, (< these are the two "knowns"), then according to Ohms Law and the formulas above, voltage equals current multiplied by resistance:

(V = 2 amperes x 1 ohm = 2 volts).

To find the current in the same circuit above assuming we did not know it but we know the voltage and resistance:
I = 2 volts divided by the resistance 1 ohm = 2 amperes.

In this third example we know the current (2 amperes) and the voltage (2 volts)....what is the resistance?
Substituting the formula:
R = Volts divided by the current (2 volts divided by 2 amperes = 1 ohm

Sometimes it's very helpful to associate these formulas Visually. The Ohms Law "wheels" and graphics below can be a very useful tool to jog your memory and help you to understand their relationship.





The wheel above is divided into three sections:

Volts V (on top of the dividing line)
Amps (amperes) I (lower left below the dividing line)
Resistance R (lower right below the dividing line)
X represents the (multiply by sign)
Memorize this wheel

To use, just cover the unknown quantity you need with your minds eye and what is left is the formula to find the unknown.

Example:

To find the current of a circuit (I), just cover the I or Amps section in your mines eye and what remains is the V volts above the dividing line and the R ohms (resistance) below it. Now substitute the known values. Just divided the known volts by the known resistance.
Your answer will be the current in the circuit.
The same procedure is used to find the volts or resistance of a circuit!

Here is another example:

You know the current and the resistance in a circuit but you want to find out the voltage.

Just cover the voltage section with your minds eye...what's left is the I X R sections. Just multiply the I value times the R value to get your answer! Practice with the wheel and you'll be surprised at how well it works to help you remember the formulas without trying!
 This Ohm's Law Triangle graphic is also helpful to learn the formulas.
Just cover the unknown value and follow the graphic as in the yellow wheel examples above.

You'll have to insert the X between the I and R in the graphic and imagine the horizontal divide line but the principal is just the same.






In the above Ohm's law wheel you'll notice that is has an added section (P) for Power and the letter E* has been used instead of the letter V for voltage.
This wheel is used in the exact same fashion as the other wheels and graphics above.
You will also notice in the blue/green areas there are only two known values with the unknown value in the yellow sections. The red bars separate the four units of interest.

An example of the use of this wheel is:
Let's say that you know the power and the current in a circuit and want to know the voltage.
Find your unknown value in the yellow areas (V or E* in this wheel) and just look outward and pick the values that you do know. These would be the P and the I. Substitute your values in the formula, (P divided by I) do the math and you have your answer!

Info: Typically, Ohm's Law is only applied to DC circuits and not AC circuits.
* The letter "E" is sometimes used in representations of Ohm's Law for voltage instead of the "V" as in the wheel above.


Learning how things work can be fun.
With this skill you can Build things.
make better use of things
and repair things..
have better job opportunities

An important part of learning electronics
is the the need to visualize the action inside a piece of equipment. In electronics things happen at a sub-atomic level. to understand what is happening, you need a mental picture, a visualization  of events you can see directly. You need a in your mind of how events are turned on and off. you need to visualize signals being amplified and attenuated. ( These are long words for being made bigger and smaller )

take an overview of electronic equipment. Inside anything what's happening can be describe as some kind of source delivering power to some kind of a load. The terms source and load become clearer as you can discover a few basics. A source is where the energy comes from. A load is what does the work. When power is delivered to a load, the load produces sound, heat, pictures or anything else that can be produced electronically..

Dow load this Tutorial Software below, In this program you will learn some useful hints about basic electronics, the program includes some exercises to have fun with....

On successful completion of this lesson you will be able to:

describe the structure of a simple atom
recognize a series resistor circuit
calculate the expected current in a series circuit
calculate the power dissipated in a resistor from color code
measure the voltage across a resistor or circuit 
measure the current through a resistor circuit
recognize several types of switches
determine circuit paths in switched circuits

A circuit composed solely of components connected in series is known as aseries circuit

A Simple Series Circuit
Let's start with a series circuit consisting of three resistors and a single battery:

The first principle to understand about series circuits is that the amount of current is the same through any component in the circuit. This is because there is only one path for electrons to flow in a series circuit, and because free electrons flow through conductors like marbles in a tube, the rate of flow (marble speed) at any point in the circuit (tube) at any specific point in time must be equal.
From the way that the 9 volt battery is arranged, we can tell that the electrons in this circuit will flow in a counter-clockwise direction, from point 4 to 3 to 2 to 1 and back to 4. However, we have one source of voltage and three resistances. How do we use Ohm's Law here?
An important caveat to Ohm's Law is that all quantities (voltage, current, resistance, and power) must relate to each other in terms of the same two points in a circuit. For instance, with a single-battery, single-resistor circuit, we could easily calculate any quantity because they all applied to the same two points in the circuit:




Since points 1 and 2 are connected together with wire of negligible resistance, as are points 3 and 4, we can say that point 1 is electrically common to point 2, and that point 3 is electrically common to point 4. Since we know we have 9 volts of electromotive force between points 1 and 4 (directly across the battery), and since point 2 is common to point 1 and point 3 common to point 4, we must also have 9 volts between points 2 and 3 (directly across the resistor). Therefore, we can apply Ohm's Law (I = E/R) to the current through the resistor, because we know the voltage (E) across the resistor and the resistance (R) of that resistor. All terms (E, I, R) apply to the same two points in the circuit, to that same resistor, so we can use the Ohm's Law formula with no reservation.
However, in circuits containing more than one resistor, we must be careful in how we apply Ohm's Law. In the three-resistor example circuit below, we know that we have 9 volts between points 1 and 4, which is the amount of electromotive force trying to push electrons through the series combination of R₁, R₂, and R₃. However, we cannot take the value of 9 volts and divide it by 3k, 10k or 5k Ω to try to find a current value, because we don't know how much voltage is across any one of those resistors, individually.

The figure of 9 volts is a total quantity for the whole circuit, whereas the figures of 3k, 10k, and 5k Ω are individual quantities for individual resistors. If we were to plug a figure for total voltage into an Ohm's Law equation with a figure for individual resistance, the result would not relate accurately to any quantity in the real circuit.
For R₁, Ohm's Law will relate the amount of voltage across R₁ with the current through R₁, given R₁'s resistance, 3kΩ:

But, since we don't know the voltage across R₁ (only the total voltage supplied by the battery across the three-resistor series combination) and we don't know the current through R₁, we can't do any calculations with either formula. The same goes for R₂ and R₃: we can apply the Ohm's Law equations if and only if all terms are representative of their respective quantities between the same two points in the circuit.
So what can we do? We know the voltage of the source (9 volts) applied across the series combination of R₁, R₂, and R₃, and we know the resistances of each resistor, but since those quantities aren't in the same context, we can't use Ohm's Law to determine the circuit current. If only we knew what the total resistance was for the circuit: then we could calculate total current with our figure for total voltage (I=E/R).
This brings us to the second principle of series circuits: the total resistance of any series circuit is equal to the sum of the individual resistances. This should make intuitive sense: the more resistors in series that the electrons must flow through, the more difficult it will be for those electrons to flow. In the example problem, we had a 3 kΩ, 10 kΩ, and 5 kΩ resistor in series, giving us a total resistance of 18 kΩ:

In essence, we've calculated the equivalent resistance of R₁, R₂, and R₃combined. Knowing this, we could re-draw the circuit with a single equivalent resistor representing the series combination of R₁, R₂, and R₃:

Now we have all the necessary information to calculate circuit current, because we have the voltage between points 1 and 4 (9 volts) and the resistance between points 1 and 4 (18 kΩ):

Knowing that current is equal through all components of a series circuit (and we just determined the current through the battery), we can go back to our original circuit schematic and note the current through each component:

Now that we know the amount of current through each resistor, we can use Ohm's Law to determine the voltage drop across each one (applying Ohm's Law in its proper context):

Notice the voltage drops across each resistor, and how the sum of the voltage drops (1.5 + 5 + 2.5) is equal to the battery (supply) voltage: 9 volts. This is the third principle of series circuits: that the supply voltage is equal to the sum of the individual voltage drops.
However, the method we just used to analyze this simple series circuit can be streamlined for better understanding. By using a table to list all voltages, currents, and resistances in the circuit, it becomes very easy to see which of those quantities can be properly related in any Ohm's Law equation:

The rule with such a table is to apply Ohm's Law only to the values within each vertical column. For instance, E_R1 only with I_R1 and R₁; E_R2 only with I_R2 and R₂; etc. You begin your analysis by filling in those elements of the table that are given to you from the beginning:

As you can see from the arrangement of the data, we can't apply the 9 volts of E_T(total voltage) to any of the resistances (R₁, R₂, or R₃) in any Ohm's Law formula because they're in different columns. The 9 volts of battery voltage is not applied directly across R₁, R₂, or R₃. However, we can use our "rules" of series circuits to fill in blank spots on a horizontal row. In this case, we can use the series rule of resistances to determine a total resistance from the sum of individual resistances:

Now, with a value for total resistance inserted into the rightmost ("Total") column, we can apply Ohm's Law of I=E/R to total voltage and total resistance to arrive at a total current of 500 µA:

Then, knowing that the current is shared equally by all components of a series circuit (another "rule" of series circuits), we can fill in the currents for each resistor from the current figure just calculated:

Finally, we can use Ohm's Law to determine the voltage drop across each resistor, one column at a time:

Just for fun, we can use a computer to analyze this very same circuit automatically. It will be a good way to verify our calculations and also become more familiar with computer analysis. First, we have to describe the circuit to the computer in a format recognizable by the software. The SPICE program we'll be using requires that all electrically unique points in a circuit be numbered, and component placement is understood by which of those numbered points, or "nodes," they share. For clarity, I numbered the four corners of our example circuit 1 through 4. SPICE, however, demands that there be a node zero somewhere in the circuit, so I'll re-draw the circuit, changing the numbering scheme slightly:

All I've done here is re-numbered the lower-left corner of the circuit 0 instead of 4. Now, I can enter several lines of text into a computer file describing the circuit in terms SPICE will understand, complete with a couple of extra lines of code directing the program to display voltage and current data for our viewing pleasure. This computer file is known as the netlist in SPICE terminology:

series circuit
v1 1 0
r1 1 2 3k
r2 2 3 10k
r3 3 0 5k
.dc v1 9 9 1
.print dc v(1,2) v(2,3) v(3,0)
.end

Now, all I have to do is run the SPICE program to process the netlist and output the results: 

v1            v(1,2)      v(2,3)      v(3)        i(v1)       
9.000E+00     1.500E+00   5.000E+00   2.500E+00  -5.000E-04

This printout is telling us the battery voltage is 9 volts, and the voltage drops across R₁, R₂, and R₃ are 1.5 volts, 5 volts, and 2.5 volts, respectively. Voltage drops across any component in SPICE are referenced by the node numbers the component lies between, so v(1,2) is referencing the voltage between nodes 1 and 2 in the circuit, which are the points between which R₁ is located. The order of node numbers is important: when SPICE outputs a figure for v(1,2), it regards the polarity the same way as if we were holding a voltmeter with the red test lead on node 1 and the black test lead on node 2. 
We also have a display showing current (albeit with a negative value) at 0.5 milliamps, or 500 microamps. So our mathematical analysis has been vindicated by the computer. This figure appears as a negative number in the SPICE analysis, due to a quirk in the way SPICE handles current calculations. 
In summary, a series circuit is defined as having only one path for electrons to flow. From this definition, three rules of series circuits follow: all components share the same current; resistances add to equal a larger, total resistance; and voltage drops add to equal a larger, total voltage. All of these rules find root in the definition of a series circuit. If you understand that definition fully, then the rules are nothing more than footnotes to the definition.

• REVIEW:
• Components in a series circuit share the same current: I_Total = I₁ = I₂ = . . . I_n
• Total resistance in a series circuit is equal to the sum of the individual resistances: R_Total = R₁ + R₂ + . . . R_n
• Total voltage in a series circuit is equal to the sum of the individual voltage drops: E_Total = E₁ + E₂ + . . . E_n

One connected completely in parallel is known as a parallel circuit.
  
Simple Parallel Circuit 
Let's start with a parallel circuit consisting of three resistors and a single battery:

The first principle to understand about parallel circuits is that the voltage is equal across all components in the circuit. This is because there are only two sets of electrically common points in a parallel circuit, and voltage measured between sets of common points must always be the same at any given time. Therefore, in the above circuit, the voltage across R₁ is equal to the voltage across R₂ which is equal to the voltage across R₃ which is equal to the voltage across the battery. This equality of voltages can be represented in another table for our starting values:

Just as in the case of series circuits, the same caveat for Ohm's Law applies: values for voltage, current, and resistance must be in the same context in order for the calculations to work correctly. However, in the above example circuit, we can immediately apply Ohm's Law to each resistor to find its current because we know the voltage across each resistor (9 volts) and the resistance of each resistor:




At this point we still don't know what the total current or total resistance for this parallel circuit is, so we can't apply Ohm's Law to the rightmost ("Total") column. However, if we think carefully about what is happening it should become apparent that the total current must equal the sum of all individual resistor ("branch") currents:

As the total current exits the negative (-) battery terminal at point 8 and travels through the circuit, some of the flow splits off at point 7 to go up through R₁, some more splits off at point 6 to go up through R₂, and the remainder goes up through R₃. Like a river branching into several smaller streams, the combined flow rates of all streams must equal the flow rate of the whole river. The same thing is encountered where the currents through R₁, R₂, and R₃ join to flow back to the positive terminal of the battery (+) toward point 1: the flow of electrons from point 2 to point 1 must equal the sum of the (branch) currents through R₁, R₂, and R₃.
This is the second principle of parallel circuits: the total circuit current is equal to the sum of the individual branch currents. Using this principle, we can fill in the I_Tspot on our table with the sum of I_R1, I_R2, and I_R3:

Finally, applying Ohm's Law to the rightmost ("Total") column, we can calculate the total circuit resistance:

Please note something very important here. The total circuit resistance is only 625 Ω: less than any one of the individual resistors. In the series circuit, where the total resistance was the sum of the individual resistances, the total was bound to begreater than any one of the resistors individually. Here in the parallel circuit, however, the opposite is true: we say that the individual resistances diminish rather than add to make the total. This principle completes our triad of "rules" for parallel circuits, just as series circuits were found to have three rules for voltage, current, and resistance. Mathematically, the relationship between total resistance and individual resistances in a parallel circuit looks like this:

The same basic form of equation works for any number of resistors connected together in parallel, just add as many 1/R terms on the denominator of the fraction as needed to accommodate all parallel resistors in the circuit.
Just as with the series circuit, we can use computer analysis to double-check our calculations. First, of course, we have to describe our example circuit to the computer in terms it can understand. I'll start by re-drawing the circuit:

Once again we find that the original numbering scheme used to identify points in the circuit will have to be altered for the benefit of SPICE. In SPICE, all electrically common points must share identical node numbers. This is how SPICE knows what's connected to what, and how. In a simple parallel circuit, all points are electrically common in one of two sets of points. For our example circuit, the wire connecting the tops of all the components will have one node number and the wire connecting the bottoms of the components will have the other. Staying true to the convention of including zero as a node number, I choose the numbers 0 and 1:

An example like this makes the rationale of node numbers in SPICE fairly clear to understand. By having all components share common sets of numbers, the computer "knows" they're all connected in parallel with each other.
In order to display branch currents in SPICE, we need to insert zero-voltage sources in line (in series) with each resistor, and then reference our current measurements to those sources. For whatever reason, the creators of the SPICE program made it so that current could only be calculated through a voltage source. This is a somewhat annoying demand of the SPICE simulation program. With each of these "dummy" voltage sources added, some new node numbers must be created to connect them to their respective branch resistors:

The dummy voltage sources are all set at 0 volts so as to have no impact on the operation of the circuit. The circuit description file, or netlist, looks like this:

Parallel circuit
v1 1 0 
r1 2 0 10k
r2 3 0 2k
r3 4 0 1k
vr1 1 2 dc 0
vr2 1 3 dc 0
vr3 1 4 dc 0
.dc v1 9 9 1
.print dc v(2,0) v(3,0) v(4,0)
.print dc i(vr1) i(vr2) i(vr3)
.end

Running the computer analysis, we get these results (I've annotated the printout with descriptive labels):

v1            v(2)        v(3)        v(4)            
9.000E+00     9.000E+00   9.000E+00   9.000E+00
battery       R1 voltage  R2 voltage  R3 voltage
voltage       

v1            i(vr1)      i(vr2)      i(vr3)          
9.000E+00     9.000E-04   4.500E-03   9.000E-03
battery       R1 current  R2 current  R3 current
voltage

These values do indeed match those calculated through Ohm's Law earlier: 0.9 mA for I_R1, 4.5 mA for I_R2, and 9 mA for I_R3. Being connected in parallel, of course, all resistors have the same voltage dropped across them (9 volts, same as the battery).
In summary, a parallel circuit is defined as one where all components are connected between the same set of electrically common points. Another way of saying this is that all components are connected across each other's terminals. From this definition, three rules of parallel circuits follow: all components share the same voltage; resistances diminish to equal a smaller, total resistance; and branch currents add to equal a larger, total current. Just as in the case of series circuits, all of these rules find root in the definition of a parallel circuit. If you understand that definition fully, then the rules are nothing more than footnotes to the definition.

• REVIEW:
• Components in a parallel circuit share the same voltage: E_Total = E₁ = E₂ = . . . E_n
• Total resistance in a parallel circuit is less than any of the individual resistances: R_Total = 1 / (1/R₁ + 1/R₂ + . . . 1/R_n)
• Total current in a parallel circuit is equal to the sum of the individual branch currents: I_Total = I₁ + I₂ + . . . I_n.