Using the bread board: multimeter, LED's, resistors

First topic was using a multimeter.  This is a device used to check continuity, resistance, voltage, and other functions.  We tested our soldering joints on the PCB board for continuity on two points.  With the multimeter, we looked at voltage.  Voltage comes in to forms: AC or DC, and is directional.  AC or alternating current is what comes out of a wall socket and DC or direct current is something like a battery.

Voltage will run through a LED light and brighten it.  The more voltage, the brighter it gets; too bright and the bulb will burn out.  For parts, next to the current a form of controlling voltage is needed-resistors.

Next is understanding resistors; these components limit how much current can flow through.  They are color coded to provide a value of how much current it takes in. 

The bread board is a great way to test the components.  Each LED has a limit to how much current it can take, so our job is to find out a proper resistor for optimal performance of the system.

First we need to know the "Voltage loop" law or KVL.  This means for any loop circuit voltage must balance: amount generated= amount used. So for a 5V battery with forward loop of 2.5V, the resistor voltage must equal 2.5V.  Thats just the voltage through the resistor.  To find the right resistor we need another law, Ohm's law.  This shows how resistors work...

Voltage across resistor(V) = current through resistor(amperes)*the resistance of the resistor(ohms).  V=I*R

We have voltage and the current is given to us, then we can find the resistor.

2.5V= .02A*R  R=125ohm.

Unfortunately you wont get an exact resistor so find one closest to it.  Also the bigger the resistors value the less current goes through which means a dimmer light and the vise-versa is also true.