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Unformatted text preview: Lecture 1 - Coulomb’s Law
Lecture Chapter 25 - Tuesday January 9th •Introduction and overview of the course
•Discussion of syllabus and policies
•Overview of the course web page •Electrostatics
•Charge and charging •Conductors and insulators •Coulomb’s Law •Scalar and vector notation
•Discrete charge distributions (superposition principle)
•Continuous charge distributions Reading: pages 567 thru 580 (chapter 25) in HRK
Read and understand the sample problems
WebAssign assignment: set 1, due Thu. 18th at 11:59pm
There is also a practice assignment (not counted in grade)
Graded problem: Ch. 25 – Prob. 10
Practice problems: Ch. 25 - Ex. 1, 9, 19; Prob. 3 & 11 The PHY2061 Course Web Site
•All information is posted here •Syllabus, homework and exam policies, etc..
•Links to on-line homework pages (incl. deadlines)
•Course schedule with exam dates
•Solutions to exams (and practice questions) •DON’T FORGET TO DO THE DAILY HOMEWORK!!
•No excuse for not getting close to 100% for the
weekly (WebAssign) homework sets
•YOU NEED TO PURCHASE REMOTES FOR THE
IN-CLASS QUIZZES (CONSULT THE COURSE
WEB PAGE) About the text book
•Many useful exercises and problems at ends of chapters
•Multiple choice questions (may be used for JiTT/HiTT)
•Conceptual questions (ask me if you do not understand)
•Exercises are similar to the example problems in main text
•Problems require thinking outside of the box •All odd numbered Exercises and Problems have the
numerical answers at the back of the text book
•I will assign a few of these problems as optional work,
and I will post solutions after the corresponding
•Take some time to study the appendices at the end of
the book. In particular, you will find integrals and other
useful trigonometric identities. The PHY2061 grading
PHY 2061 (spring 2005/2006)
8 Mean = 75%
Median = 80%
50% of class scored above 80%
70% of class scored above 70% Number of students 6 B+ 2 years of 2061:
Note 82% A/B+/B B
C 4 2 F D 0
20 30 40 50 60 70 80 90 100 Score (%) •DON’T FORGET TO DO THE DAILY HOMEWORK!!
•YOU NEED TO PURCHASE REMOTES FOR THE INCLASS QUIZZES (1ST TRIAL ON THURSDAY).
•ON-LINE HOMEWORK. DO THE HOMEWORK & COME TO CLASS
100 PHY 3513 (Fall 2005) • Clear correlation
and exam scores.
• Nevertheless, the
you will not get away
with memorization of
homework problems. Overall Grade 90 80 70 60 50 40
20 30 40 50 60 70 80 90 100 110 Score on Homework •IF YOU ARE HERE ONLY FOR THE GRADE, THE
CHANCES ARE HIGH THAT YOU WILL DO POORLY.
•THIS IS AN ENRICHED COURSE – YOU ARE HERE TO
LEARN. PHY2060 - What causes acceleration?
• Some sort of interaction - loosely speaking, a push or a
pull on an object.
• We call this a force, which can be said to act on a body.
• Examples of forces:
Normal or "contact force"
Weak and strong nuclear forces We'd better be more
scientific about this... The main subject of this course
ex Test charge Charges of the same sign repel
one another, charges of opposite
sign attract one another. What is charge?
•Charge is measured in Coulomb’s (C) • Fundamental unit.
• Definition based on forces between current carrying
wires (current = Ampères, or C/s), i.e. chapter 33. •Charge is discrete • Thompson discovered the electron in 1896. He found
that charge was carried by elementary particles with
the same charge to mass ratio.
• The elementary charge of the electron was not
measured until 1909 (Millikan).
• Both experiments earned Nobel prizes. Charge on an electron:
1 Coulomb of charge:
1 Ampère (= 1 C/s)
Charge is discrete: e = 1.6 × 10−19 Coulombs
6.24 × 1018 electrons
6.24 × 1018 electrons/second
q = ne n = ±1, ±2, ±3,... Static electricity through charging
Insulator Electrical discharge
Electrical Methods of charging
Methods Coulomb’s Law
Coulomb Coulomb’s torsional balance
Coulomb 1785 q1 q2
r K= 1
4πε o or q1 q2
r2 = 8.99 × 109 N ⋅ m 2 / C2 εο = 8.85418781762 × 10-12 C2/N·m2 1
4π × 10−7 N ⋅ s2 / C2 ) × c 2
c = speed of light in vacuum
= 299792458 m/s “Electrodynamics in a nutshell” 1 qQ
4πε o r ˆ
Mix in a little
relativity q Q ∫ E ⋅ dA = q εo dΦB
∫ E ⋅ d s = − dt ∫ B ⋅ dA = 0
∫ B ⋅ d s = μoi + μoε o dt Coulomb’s Law in vector notation
Coulomb 1 q1q2
r12 = − F21
4πε o r12
4πε o r21 r12
r12 Superposition principle
charges Test charge q0
Fq0 = F1 + F2 + F3 + ...Fi = ∑ Fi
i •Leads to Maxwell’s equations being linear. Calculus (continuous charge distribution):
F = ∫ dF = iˆ ∫ dFx + ˆ ∫ dFy + k ∫ dFz
j 1 q0dq
4πε o r q0 = test charge ...
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