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19-04-10, 04:01 AM
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....

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..


Dowload 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


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19-04-10, 04:19 AM
Ohm's Law

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 thatcomes 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.


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!
http://www.hamuniverse.com/ohmslaw1.gif 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.

19-04-10, 04:24 AM
Parallel Circuit

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:
http://sub.allaboutcircuits.com/images/10070.png 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 IT spot on our table with the sum of IR1, IR2, and IR3:
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 be greater 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:
http://sub.allaboutcircuits.com/images/00095.png 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)
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
These values do indeed match those calculated through Ohm's Law earlier: 0.9 mA for IR1, 4.5 mA for IR2, and 9 mA for IR3. 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.

Components in a parallel circuit share the same voltage: ETotal = E1 = E2 = . . . En
Total resistance in a parallel circuit is less than any of the individual resistances: RTotal = 1 / (1/R1 + 1/R2 + . . . 1/Rn)
Total current in a parallel circuit is equal to the sum of the individual branch currents: ITotal = I1 + I2 + . . . In.