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Welcome to PHY212!!General Physics II:!
Electricity, Magnetism, and Light!
Prof. Mitch [email protected]
Lecture 1.1!Jan. 13, 2015
Announcements
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• Register for PHY222 (labs) if you haven’t already!!!!‣ PHY212 and PHY222 are separate courses.!
‣ PHY222 IS A REQUIRED CO-REQUISITE COURSE !
‣ PHY222 will NOT be meeting this week !
• Let’s review the course syllabus:!
https://msoderbe.expressions.syr.edu/phy212-s15/files/2015/01/PHY212_Spring2015_Syllabus.pdf!
• I will post course content in both Blackboard and on http://msoderbe.expressions/syr.edu/phy212-s15 . I will put lecture slides and recordings on the expressions site, usually the same day of the lecture.
Homework and Recitations
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•Your first Homework assignment(s) are posted in Mastering Physics.!‣HW0 is a questionnaire. Complete it, and you get a 100%.!
‣HW1 is your other assignment for the week. It consists of questions from the text.!
•You will work in groups of 3 or 4 during recitation (a.k.a. - workshops) on selected problems. One group member will present their solution to the whole section. All problems assigned during recitation are fair game for quizzes/exams.!•Read the relevant textbook sections before recitation.!•Your recitation grade is based on attendance and participation. !•TAs will discuss further details with you when you start tomorrow!!•Show up for your recitations prepared - Bring calculator, textbook, paper, pencil, etc...
Tips for Success
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•The number one suggestion I can offer to you for a successful PHY212 experience is that you spend adequate time studying the course material, and try to solve as many problems from the textbook as you can. !‣If you make this investment, it will pay off come quiz/exam time.!‣I have no doubt you can find solution manuals for Knight online…you will
not LEARN anything by just copying them down and plugging in numbers to do your Mastering Physics assignments.!
•If you find yourself struggling with the course material, PLEASE come see me in my office so I can help you out.!•The recitations are meant to be “study halls”, where you will have time to practice problems similar/identical to those you’ll find on homework/quizzes/exams. Use this time wisely.
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Lecture 1.1 :! Introduction to Electric Charge
Lecture Outline:!Motivation!
Model of Electric Charge!Insulators and Conductors!
Textbook Reading:!Ch. 25.1 - 25.3
Motivation
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The study of Electricity and Magnetism in modern form has been around for over 100 years. Perfect example of how studying something esoteric can revolutionize the word.
Motivation
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•Our natural world is awash in electric and magnetic phenomena.!
•Understanding this phenomena, and developing theories of it that can be applied in other domains, is the bread and butter of many scientists and engineers.
Why are Electricity and Magnetism important?
Motivation
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Applications of Electricity and Magnetism are too vast to enumerate...all of you probably have at least one
electronic device on you right now!
Why are Electricity and Magnetism important?
Motivation
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The theoretical underpinnings of electromagnetism are quite beautiful, and helped lead scientists down the path to our
present-day understanding of “modern physics”.
Why are Electricity and Magnetism important?
Text
Motivation
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What are the overall goals for this course?
1.To develop a basic understanding of the laws of electromagnetism.!2.To develop the ability to apply these new concepts to physical situations.!3.To develop an appreciation for the role that electromagnetism plays both
in our modern society and in the universe.!
Magnets?Maxwell’s Equations
CLICKERS!
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1. Determine how well you are following the subject matter. !
2. Keep you awake. If you answer (most) clicker questions, and you answer them (mostly) correctly, final grade is boosted. Maximum of 2% boost to final course grade if you do well.
I will be using data obtained from your answers to clicker questions to:!
CLICKERS!
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1. Register your clickers using Blackboard: https://answers.syr.edu/display/blackboard01/Registering+a+TurningPoint+Clicker+in+Blackboard!
2. We will be using channel 41 for clicker polls. At beginning of lecture, press: “Ch+4+1+Ch” on your clicker.
Clicker Question #1
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Who do you think will win the Superbowl?!
A B C D E
Clicker Question #1
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Who do you think will win the Superbowl?!
A B C D E
Model of Electric Charge
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We discover electric charge at a young age!
Model of Electric Charge
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As scientists, we want to understand what’s going on, so we experiment:!
Model of Electric Charge
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As scientists, we want to understand what’s going on, so we experiment:!
Model of Electric Charge
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As scientists, we want to understand what’s going on, so we experiment:!
Model of Electric Charge
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As scientists, we want to understand what’s going on, so we experiment:!
Model of Electric Charge
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1.Friction/rubbing can sometimes charge an object.!2.There are only two kinds of charge. !3.Two objects of like charge (plastic/plastic or glass/
glass) repel each other. Two objects of unlike charge (plastic/glass) attract each other.!
4.The magnitude of the force increases as the quantity of charge increases, and decreases as the distance between the charges increase.
If we did a systematic study of electric charge and its properties, we would find:!
Model of Electric Charge
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Electric Charge is a property of matter.
• e = fundamental unit of electric charge (not defined yet).!
• Protons are TIGHTLY bound in nucleus – they don’t go anywhere.!
• Electrons are more loosely bound.!
• Object Charge (q) = Npe - Nee = (Np-Ne)e
Model of Electric Charge
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Electric Charge is conserved.
• The algebraic sum (taking the + or – sign into account) of all electric charges in any closed system is constant.!
• Electrons and protons are not created out of nothing, or destroyed into nothing.!
• Neutral objects have no net charge.
Clicker Question #2
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Before charging, both rods have identical mass.
After charging:!A) plastic (on the left) has more mass!B) glass (on the right) has more mass!C) both have identical mass
Clicker Question #2
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Before charging, both rods have identical mass.
After charging:!A) plastic (on the left) has more mass!B) glass (on the right) has more mass!C) both have identical mass
Insulators and Conductors
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• Conductor – electrons move easily from one part of material to another (examples: copper wire, many metals, graphite,...)!
• Insulator – electrons are relatively fixed in place, can be moved with effort (examples: rubber, glass, plastics, air,...)
Insulators and Conductors
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Clicker Question #3
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What happens when a charged object is brought near an isolated neutral conductor
(such as a soda can)?
A) Nothing!B) Soda can is attracted to object!C) Soda can is repelled from object
Clicker Question #3
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What happens when a charged object is brought near an isolated neutral conductor
(such as a soda can)?
A) Nothing!B) Soda can is attracted to object!C) Soda can is repelled from object
Insulators and Conductors
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Excess charges within a conductor quickly arrange themselves to achieve electrostatic equilibrium.
The neutral conductor becomes polarized.
Insulators and Conductors
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How do neutral insulators respond when a charged object is brought nearby?
Charge does not easily move around in an insulator, so this must be different than what happens for conductors.!
Insulators and Conductors
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The individual atoms within an insulator become polarized when a charged object is brought
nearby , forming an electric dipole.
Since the charged object pulls more on the opposite-sign end than it pushes on the same-
sign end, there is an overall attractive force.
Reminders
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•Show up prepared for recitation session tomorrow.!•If you haven’t already, begin reading Ch. 25. You
should read the whole chapter before Thu.!•Register for Mastering Physics. Don’t wait until
Monday night!!•Work on HW0 and HW1 in Mastering Physics.!•Please come see me if you have any issues/
questions. Office hours: Tue. 3-5pm in Room 331.
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