What is an LED?

An LED is light emitting diode used to produced light in different color a common led use’s 3 Volt

to produce light, a good thing about led is that they last longer up to 30%  then any other light bulbs and uses 10% of the power.led comes in many different shape’s, size’s and color an led has two terminal for positive and negative current if  you connect the positive terminal to an negative one it wont light up so you need to connect it in the right way so it light’s up,the symbol of an led look’s like this

the symbol of an led is the same of an diode the only difference is the two aero is pointing in upward direction sometimes there is one aero  but that doesn’t matter if the user know that is an led in fallowing diagram you can see the terminal and the inner part’s of an led the longer terminal represented as anode is positive and the shorter terminal represented as cathode is negative so if you provide the current in this order it would light up other wise it wont.an led chip is basically a Diode which has two end points one for + & – , when the diode lights up the lens focus the light in the up direction, the first LED was made in the back in the 1907 , it uses silicon carbide to produce light the person attach an positive lead at the end of the silicon carbide and attach a needle and then touched it to silicon carbide so he can get a bright Spot.

lets make something that lights up

this is a very simple circuit to build the it uses a resistor of 100 ohm and 5 volt battery connect every thing in place and it would light up.

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Transistors

A Transistor  is semiconductor material made up of silicon it is used in two different ways to amplify current and to switch current on and off, for example to convert a small amount of sound into a much larger one we would use transistor to amplify the current but to switch a current on and off is different way to handle the current a Computer micro-processor use million of tiny transistors together to perform much higher complex functions such as processing displaying information.Visually transistor can be classify into two groups depending upon the volume,Small signal transistor to handle low power application and, Power Transistors to perform higher power application.Every transistor has three terminals.

There are also two types of transistor depending on the inner structure and how they controlled the current they are Bipolar junction transistor & Field effect transistor.

Field effect transistor or FET for short  FET are controlled by voltage and use no input Current,there are two types of FET that you may run into are JFET and MOSFET.

                       

Bipolar junction transistor or BJT for short bipolar are controlled by applying current to the base terminal which then controls the flow of charge between the collector and the emitter the aero in the transistor indicates the direction of the positive charge flow,FET and Bipolar are available in two Types NPN & PNP,a npn bipolar is a switch whic is open it wont conduct until current is applied in the base terminal and pnp works in the oppsite way of NPN.

Lets make something ?

this is an joule theif  it is a very useful gadget and very low cost circuit to build it takes small amount of current and convert into much larger one to light up the led.