PHYSICS 1E03 Dr. W. Okoń Office: ABB-150 e-mail: okon@physics.mcmaster.ca Class: Mon/Wed 5:30pm (no Thur class) for now… Office Hours: Tues 12:30-1:20 and 2:30-3pm Wed 11:30am-12:30pm Course web page – I will be posting news and all lecture notes here: http://physwww.mcmaster.ca/~okon/1e03/1e03s.html Textbook: Serway (any edition is OK)
Components of the course - Quizzes 10% Labs: 15% Participation (i-clicker) 5% One term tests, 90min. Total 20% (MC + long) Final exam, 3 hours. 50% (MC + long) Tutorials start this Friday: 10:30am to 12:20 in BSB-B155 Test – TBA (early April) Exam – TBA (around last day of classes) Rooms – TBA
Homework + Doing Well Download and print the lecture notes in Power Point format from the my web page. Bring the notes for class and add your own notes to them during the lecture. Read the textbook, either just before or just after the lecture, and add to your notes as you read. Try to solve all the assignment problems, these are very helpful for the tests! A list of suggested problems from the textbook is posted as a file. You can download and print these. As we cover the material from the textbook you can try to do the appropriate questions from this list if you’re done all the assignments. Do NOT work alone, find someone to solve the problems with and talk about them/physics. For the multiple choice type questions, look at the Quick Quizzes in the textbook, and old tests online.
PHYSICS 1E03 I. Electrostatics (4 weeks) II. DC Circuits (2 weeks, plus labs) III. Magnetism (3 weeks) IV. Waves (3 weeks) -includes electromagnetic waves
Introduction Gravity - a force between masses How do things interact? Gravity - a force between masses - holds planets in orbit, etc. Electromagnetism - a force between charges - responsible for all familiar forces (except gravity) – friction, normal, magnetic Weak Nuclear Force - decay of particles Strong Nuclear Force - holds nuclei together
Electric Charge + + - - + REPEL REPEL ATTRACT Units: coulomb, C A scalar quantity Comes in “positive” and “negative” + + - REPEL - REPEL + ATTRACT Units: coulomb, C and also “smallest unit of charge”, e 1.60210-19 C
Electric Charge (continued) Charge appears in nature in units of “e”: eg: Particle Charge electron -e proton +e Net charge is a conserved quantity: that is, the algebraic sum of positive and negative charges is constant. Eg +5e-3e = +2e = +8e-6e
Insulators: charges do NOT move eg: glass, rubber, paper - can be charged by rubbing, but charges do not move Conductors: (some) charges move freely eg: metals, some liquids Semiconductors: electrical properties between insulators and conductors eg: silicon, germanium
Quiz The conductor is neutral (no net charge). When a charged rod is brought close to it (without touching) the net force on the conductor will be: + - - - attractive repulsive zero it depends whether the rod is positive or negative - - - Conductor
Coulomb’s Law Point charges exert forces on each other: is a unit vector parallel to r (Coulomb’s constant)
Electric Force How/why do the electric charges repel/attract? What mediates the force? The charges exchange ‘virtual photons’ that are longitudinally polarized The theory that fully explains this interaction is called quantum electrodynamics (QED)
Example 1: Find the magnitude of the force between the charges +10 C and -5 C separated by 20 cm.
Example 2: GIVEN: Identical Masses, m=1.0 gram Equal charges q L= 60 cm FIND: Charge, q L L m m q q (equilibrium)
Quiz: ? ? What happens to each angle if the charge on the left is doubled, and the other one is halved? Assume mass of charges is small compared to mass of ball. L ? ? L m m 2q q/2 (equilibrium)
Finding Resultant force vector: 300mm 400mm Find: Force (vector) on q3 , in Cartesian form.
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