4841 Transistor

P= P-type (hole)             A= Anode
N= N-type (electrons)    K= Cathode


DIODE

TRANSISTOR

A transistor is a component used to amplify and/or a switch by using small electric signals.

NPN= Not Pointing In
PNP=Point iN Plz


How it works
To work as a amplifier a high voltage can be pass through the collector (input) and emitter (output) the base is the switch a voltage less than 1v can be use (but not more than 15v or else the transistor will over heat and melt) when base gets a signal, this allows voltage to pass from collector to emitter this acts as a amplifier. 
You can also get transistors that will turn off when base gets a signal these are PNP type transistor.


How to test
Tools need :multimeter on diode test 
There are six positions you should place with your multimeter probe to get a conclusion.
Like a diode, current will only go one way the leg that gives a reading with the two other leg is the base. now that you have found base next is to find emitter, keep one probe on base and with the other test the other two leg and the highest reading out of the 2 leg is the emitter.