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# Electricity Chapter 23-26 More notes PHYS 2020

Marketplace > Tennessee State University > Physics 2 > PHYS 2020 > Electricity Chapter 23 26 More notes
TSU
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These notes cover great exam material over electricity and electrostatics for a physics 2 course. These materials have been reworded in my own words and I have used them to completely understand el...
COURSE
Physics 2
PROF.
Dr. Geoffrey Burks
TYPE
Study Guide
PAGES
13
WORDS
CONCEPTS
physics 2, Physics, physic, Physics II, Science, Engineering, ENGR, PHYS 2010
KARMA
50 ?

## Popular in Physics 2

This 13 page Study Guide was uploaded by Lauren Adams on Sunday January 31, 2016. The Study Guide belongs to PHYS 2020 at Tennessee State University taught by Dr. Geoffrey Burks in Fall 2014. Since its upload, it has received 63 views. For similar materials see Physics 2 in Physics 2 at Tennessee State University.

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## Reviews for Electricity Chapter 23-26 More notes

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Date Created: 01/31/16
Electricity - Chapters 23-26 Saturday, September 27, 2014 10:56 PM Chapter 23:Understanding Electric Potential Since the electric force in an electric field can cause charged particles to move, it is said that the electric field is capable of  doing work. Now remember from Mechanics, that the work done by a conservative force is equal to the decrease in net potential energy? This concept still works for electricity: So, the work done on a positively charged particle by a uniform electric field is given by K 1+ U 1= K  2 U  2here K is the kinetic energy and U is the potential energy. Usually in electrostatics we are concerned mostly with the electric potential energy.    When a positive charge moves in the direction of the electric field, then the field does positive work on the charged particle and  the potential energy decreases. Think about it like this: The electric field of a positive charge already goes away from the  charge, where the magnitude is lesser. If the positive charge moved away from the electric field, the potential energy would  increase because it is going against the electric field, towards the greater magnitude.  Look at this intuitively: If you moved in the direction of a force, the force does positive work on you.  When a negative charge moves in the direction of the electric field, then the field does negative work and the potential energy  increases. This is because the electric field for a negative charge moves toward the charge, where the magnitude is greater. If the negative charge were to move away from the electric field, the potential energy would decrease since it is going against the  electric field towards a lesser magnitude.  For like charges, the closer you get, the higher the potential energy; U > 0. For unlike charges, the closer you get, the lower the potential energy; U < 0.   Electric Potential Energy is an easier concept than electric field because it is a scalar value, not a vector quantity. You can  calculate it pretty easily as well. It can be easily calculated by: For a collection of charges, the work needed to assemble them is the same as the total electric potential energy of those charges:   Electric Potential The electric potential due to a point charge at any distance from the charge is given by: Corona discharge is when charge builds up until potential difference is really big and the air around it ionizes. An example of  this is: If you want to make it harder for lightning to hit a pole, make its radius bigger. The electric potential will go up until it  hits the surface of material. The picture below is an example of corona discharge.  Another cool thing to know about electric potential is equipotential surfaces, as shown below as blue circles.  Equipotential surfaces and coronas are  Interesting ways that we can see the magnificence of electricity in nature.  Important things to know about Equipotential surfaces They are always circular, always perpendicular to the direction of the electric field, they are close when the magnitude of the  electric field is big, and they are further apart when the electric field is smaller.    With negative charge, the potential goes down. With positive charge potential goes up. At surface of a conductor, the electric  field is always perpendicular to the surface. The potential anywhere on the surface of a conductor is constant. Potentials are  helpful in finding the electric field with partial differentiation of potential: We'll see that understanding the potential difference is a very important concept in dealing with circuits.                                          Chapter 24: Capacitance and Dielectrics A capacitor is any two conductors separated by an insulator with a space in between them. Their main purpose is to store  charge. The plates conductors have an equal and opposite charge on them, creating a potential difference between the plates.  The simplest type of capacitor is the parallel plate capacitor. Basically, we pretend they have two square areas with a space a  distance away from each other and in the area in the middle the electric field is constant and perpendicular. When the separation of plates is small compared to their size, the electric field lines become straight and perpendicular. Since the plates are  oppositely charged, they are going to be attracted to each other and want to be infinitely close to each other. THIS IS A BAD  IDEA‼ This will cause the capacitor to short out and not work. Thus, we must separated them with an insulator, called a  dielectric. A dielectric allows for the capacitor plates to be super close to each other without touching. It also has the negative  effect of decreasing the potential difference between the two plates, due to the insulator between them.  The measure of the ability of a capacitor to store charge is called its capacitance.  In order to measure the capacitance of a  Capacitor, it is necessary to understand circuit diagrams. Circuit diagrams are really difficult  to visualize in real life, but take it slow, and  you'll be on the road to success in no time!  Remember that the capacitance is given by the following formula: Capacitors in series To be in series means that there is only one path to follow to get to each circuit component. When capacitors are in series, they  all have the same charge but their potential difference is split up, and they add together to get the total voltage of those circuit  components.    Capacitors in parallel                   To be in parallel means that there are multiple paths to follow to get to each circuit component. When capacitors are in parallel,  they all have the same potential but their charge is split up, and they add together to get the total charge of those circuit  components.    In circuit diagrams, the wires have the same potential as what they are touching. A surface effect happens with a dielectric  which makes it get induced charges between the plates causing less voltage but more capacitance. C goes up if you add a  dielectric. A capacitor with a dielectric has a reduced potential difference but has an increased net charge and capacitance.   Chapter 25: Resistance, current, electromotive force       When thinking about resistivity and resistance, look at it like this: The resistivity is the property of the object, say, the wood.  The resistance is the actual object, the desk.    OHM'S LAW This is the most important formula this semester! REMEMBER IT LIKE F=MA!!!!!!!!! Materials that obey Ohm's law are ohmic. Materials that do not obey Ohm's law are non­ohmic.    Chapter 26: DC Circuits Resistors Resistors in series Remember: To be in series means that there is only one path through each circuit element. When resistors are in series, the  current through all the resistors is the same. But they can have different voltages. Since the resistance is constant, the charge  cannot build up in a resistor. Resistors do not have charge EVER. There is a potential drop between each resistor, from one  end of a resistor to another. The equivalent resistance is the algebraic sum of each resistor's resistance:  Resistors in parallel Remember: To be in parallel means that there are multiple paths to each circuit element. When resistors are in parallel, the  voltage is the same across each resistor. They can have different currents. The current splits when resistor goes parallel. Since  the voltage drop must be the same across the resistors, the current will be stronger for a weaker resistor, and weaker for a  stronger resistor. Remember, the current just goes through a resistor. The equivalent resistance is the algebraic sum of the  reciprocal resistances: So

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