text: physics for scientists and - uw-madison department of physics · meet the physics 202 team...
TRANSCRIPT
Today’s Topics
Text: Physics for Scientists and Engineers -- Tipler and Mosca 6, Vol II
The Physics 202 Team
Course Formality and Overview
Electric Charge, Coulomb's Law Physics 202 Homepage
http://www.physics.wisc.edu/undergrads/courses/spring10/202/
Physics for Scientists and Engineers -- Tipler and Mosca 6, Vol II
DO NOT BUY HARD COPY OF TEXTBOOK FROM THE BOOKSTORE. Access Webassign + ebook (with link to buy hard copy of text (volume 2) for $25) by going to: http://webassign.net You will get email instructions for logging into webassign.
Meet the Physics 202 Team Faculty (instructors):
☻ Prof. Susan Coppersmith [email protected]
Research: condensed matter Office hrs: by appointment, 5334 CH, 262-8358
☻ Prof. Bruce Mellado [email protected]
Research: experimental high energy physics Office hrs: by appointment, 4223 CH, 262-8894
Meet the Physics 202 Team Teaching Assistants (labs, discussion):
Office hours: in 2307 CH (starting Jan 25). Schedule: http://www.physics.wisc.edu/undergrads/courses/spring09/202/consult.htm
Physics 202 Course Composition Lectures: TR 8:50 am (Lec. 1), 9:55 am (Lec. 2)
Labs: Mandatory. Each missing lab = - 0.5 grade pt. 10 labs total. grading: weekly lab quizzes, 2 lab reports
Start on January 25th
Discussion Sections: 2/week. grading: discussion quizzes (5 total during the semester), participation,…
Start on January 19th
Exams: 3 midterms + final (word problem format)
Homework: ~7-10 problems/week, web-based Online homework system: Webassisn http://www.webassign.net/ tutorial + end-of-chapter problems
Exams and Exam Policy Exam Dates
– Midterms: (5:30-7 PM, rooms TBA) • Exam 1: Wednesday Feb 17 • Exam 2: Wednesday March 17 • Exam 3: Wednesday April 21
– Final: Monday May 10 (5:05-7:05 PM, rooms TBA) Cumulative
If you have an academic conflict with the exam dates, inform the professors and your TA ASAP (at latest: 2 weeks before the exam period) so that we can accommodate you.
(Exam policy details on course website)
Physics 201, 202 and 249
Light and Optics
Electromagnetism
Classical Mechanics Laws of motion Force, Energy, Momentum,…
Oscillation and Waves
Relativity
Atomic Structure
Sub-Sub-Atomic: Elementary Particles
Cosmology
Many-Atoms: Molecules, solids
Sub-Atomic: Nuclear Physics
Modern Classical
201
202 249
Quantum theory
Physics 202 • Electromagnetism
– Electric force, field, and potential: stationary charges (electrostatics)
– Current, capacitance & resistance – Magnetic force and field: steady currents
(magnetostatics) – Time-dependent fields: Maxwell’s equations – Electromagnetic waves, wave motion, superposition – DC and AC Circuits
• Light and Optics – Light as rays: Geometric optics, imaging – Light as electromagnetic waves, interference
Chapter 21: Electric Charge and Field Today: Electric charges
Fundamental units of charge Conductors and insulators
Electrostatic force: Coulomb’s Law
Next Thursday: Electric Field
Calculating electric fields from charge distributions Motion of charged particle in external electric field
Please read Ch. 21 before Thursday’s lecture
Properties of Electric Charge 2 types: positive or negative* SI Unit: Coulomb (C). 1 C= chg of 6.24x1018 protons Building blocks of matter:
Electric charge is quantized: q=±Ne (e=1.602x10-19 C) Electric charge of isolated system is conserved *neutral objects: no charge or equal amount of + and -
Charge (C) Mass (kg) Electron -e=-1.602x10-19 9.11x10-31
Proton +e=+1.602x10-19 1.673x10-27
Neutron 0 1.675x10-27
Conductors v. Insulators
- - - - - - - + +
+ + + + + +
+ + + +
+ + + +
Electroscope (next lab)
charge also by induction!
Conductors (metals…):
charges free to move
Insulators (glass, plastic, rubber…):
Consider how charge is carried on macroscopic objects. In Physics 202, we are concerned with only 2 types:
charges NOT free to move
Neutral metal
+ + + + + + ++ + + + ++
+++
+- - -
-
-
Positively charged rod (too few electrons)
+ + + + + + +
Less positively charged rod
+
+++
+
Positively charged metal
+ + + + + + ++ + + + +
+
+++
+- - -
-
-
electron flow
Charging by conduction (touching)
Charging conductors by Induction
• Charging by induction requires no contact with the object inducing the charge
a) We start with a neutral metallic sphere
b) The rod does not touch the sphere. The electrons in the neutral sphere are redistributed
charged rubber rod a) b)
Coulomb’s Law Electric Force b/w 2 stationary point charges:
(Coulomb’s Law)
Coulomb Constant: k = 8.987x109Nm2/C2 = 1/(4πε0) ε0: permitivity of free space = 8.85x10-12 C2/Nm2
Attractive (opp sign charges), repulsive (like sign charges)
+ - + - + + - -
F =kq1q2r2
Four fundamental forces: Strong > Electromagnetic > Weak >> Gravitation