Unit 6

This unit is all about charges and electricity.  First lets talk about the most basic aspect of electricity, Charges.  

Charges:  Come in two types.  Negative - and positive +.  If something has more negative charges then that object is itself considered to be a negatively charged.  Likewise if an object has more positive charges it will be positively charged.  However, when there is a balance of + and - charges the object is considered neutral.   

One more curious aspect of charges is that like charges repel each other   -    -         +      +

and that opposite charges attract each other   -+     

       There are three ways that an object can obtain a charge.

1) Direct contact. This occurs when two objects have a point of contact and electrons are transferred.

2) Friction.  This occurs when two objects rub against each other and one object will steel electrons from the other.

3) Induction.  this occurs when objects do not touch, but the force is great enough that the charges move into the other object. 

     Another important charge related thing is polarization.                    Polarization is what occurs when the charges in an object move to opposite sides of an object.  What this results in is the object becomes charged because there is an imbalance between the -  and + charges  in the object.  

Coulomb's law:  F=kq1q2/d^2

Hey wanna hear something shocking?  ELECTRICITY!!!! 

But really electricity is pretty cool.  The way that we measure electricity is in Amps  A.
Electricity flows in circuits like the ones that we used in class to light the light bulbs. 

In the picture above the light bulb lights up because it is connected to a completed and unbroken circuit.  This allows electricity to flow to the bulb.  But hold up. Why does electricity flow?   

Well this all has to do with voltage.  When there is a difference in potential energy, a voltage is induced.  this results in the flow of electricity called current.   

                                     Voltage = V 

                                     Current = I 

Ok, so back to the circuits.  Circuits themselves come in two types, series and parallel.  

Series circuits have one path for current to flow.  This means that when one portion of the circuit is broken, the whole thing fails.  

   

Parallel circuits have multiple paths for the current o flow.  This is helpful because it means that when one part fails, the rest of it can keep going.   

In things such as buildings, where electricity needs to go to multiple places, parallel circuits are very useful in that they allow certain things to have no current, and others to have current. All while keeping a complete circuit. 

The wires that make up circuits have differences in thicknesses and lengths.  And what this causes is varying resistance, 

 

                                               Increased length/thickness = increased resistance. 

Resistance = R

 

                                        The formula for current: I =V/R