Charges and Electricity Reflection

Charges and Polarization including Coulomb's law

Coulomb's Law

F=k(q1q2/d2)

Why does your hair stand up when you take off a hat?

Hat and hair charged by friction. The like charges repel each other and make the hair on your head stand up

Induction? Other ways to charge things?

Induction steals the electrons from an object and makes the object positively charged. Friction and contact are the other ways of charging.

The Difference Between AC and DC

AC stands for 'alternating current'. This means that the current will alternate directions.
DC stands for 'direct current'. This means that the current will keep the same direction throughout.

What is Voltage?

Potential Difference.

Change in PE/ charge

V=(change in PE)/q

Units
Volts (V) = Joules/Coulomb

Energy given to each Coulomb of charged, measured across two points.

What is current?

current is the flow of charge

Units
Amps (A)= Coulombs/second

Current goes through the circuit

What is Resistance?

Resistance is the resistance to the flow of charge.

Unit
Ohms (omega symbol)

Things to Remember:

The electrons that flow are already in the circuit. The actual speed of electrons is extremely slow (think snail's pace).

The Energy/Electric Field travels at neat the speed of light (NOT the electrons themselves... REMEMBER!!! Snail's pace!!)

When something is charged, it means that there is a 'imbalance of protons vs. electrons. To charge an object, charges must be transferred.'

There are 3 methods of charging:

1.) Contact

2.) Friction

3.) Induction

When something is Polarized it means that the the charges within an object have rearranged themselves and that the Net charge still equals zero. This does not mean that the object is now charged.

Electronic Shielding 

(Electric field/ Electric force inside a conductor=0)

Ohm's Law is V=IR

Coulomb's Law

F=k(q1q2/d*2)

The changes in distance affect changes in force shown by:

2d=1/4F and 1/2d=4F

Power=VI

Different filaments have different resistances. The resistance of something can increase in three ways:

1.) longer

2.) thinner

3.) both longer and thinner

What was difficult for me this unit was my organization, or more realistically the lack-there-of. my non-existent organization this unit is making my efforts in studying harder and harder. Next unit, I really need to make a designated binder to keep my quizzes, notes, and handouts in. My poor organization skills are going to kill my grade.

http://goblues.org/faculty/lawrencel/files/2012/08/ONQ-6-2-Answers1.pdf

http://goblues.org/faculty/lawrencel/files/2012/08/ONQ-6-1-Answers.pdf

Ohm's Law

This cartoon helps me remember that Ohm's law has to do with resistance. V=IR is the equation for Ohm's law. V= voltage, I= current, and R= resistance.

Units for V, I and R

The Filament in a light bulb is what gives resistance. The thinner, longer or both thinner and longer the filament is, the more resistant it will be. Resistance also increases the hotter it gets.

Voltage Resource

In this video, the person speaking makes clear some very important points about voltage.

• V= Potential Energy/q
• When you are dealing with volts, you are specifically dealing with energy
• and it is energy per charge
• 1 Volt= 1 J/C
• deals with 2 points

I really liked how he said "when we push, from A to B, we are exerting a force through a distance... We are expending energy, and the energy that we expend goes into potential energy and stored as electrical potential energy... There is more Potential Energy at point B then it had at point A." This was really helpful to hear and see him drawing it out. His comparison between gravity and electrical current was very helpful as well (when he is talking about the toaster). I wish he did more with solving problems, though. Pretty helpful, though, with getting the main ideas down.