# PHYSICS 1E03 Dr. W. Okoń Office: ABB-150 Class: Tue/Thu 9-12 (June 26 th class in JHE 376) Office Hours: Tue/Thu 12:15-1:15pm.

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PHYSICS 1E03 Dr. W. Okoń Office: ABB-150 e-mail: okon@physics.mcmaster.ca Class: Tue/Thu 9-12 (June 26 th class in JHE 376) Office Hours: Tue/Thu 12:15-1:15pm 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 - Labs: 15% - Participation (i-clicker) 5% - One term tests, 90min. Total 30% (MC + long) - Final exam, 3 hours. 50% (MC + long) Test Rooms – TBA Labs – 1 st lab will be this Thursday, the others will be on Tuesdays as scheduled. Labs – we will automatically replace your lab mark with your old mark if you have done ALL of the labs previously

PHYSICS 1E03 I.Electrostatics II.DC Circuits III.Magnetism IV.Waves

Introduction 1)Gravity - a force between masses - holds planets in orbit, etc. 2)Electromagnetism - a force between charges - responsible for all familiar forces (except gravity) – friction, normal, magnetic 3)Weak Nuclear Force - decay of particles 4)Strong Nuclear Force - holds nuclei together How do things interact?

Electric Charge A scalar quantity Comes in “positive” and “negative” + + - + - - REPEL ATTRACT Units: coulomb, C and also “smallest unit of charge”, e   1.602  10 -19 C

Electric Charge (continued) Net charge is a conserved quantity: that is, the algebraic sum of positive and negative charges is constant. Eg +5e-3e = +2e = +8e-6e Charge appears in nature in units of “e”: eg:ParticleCharge electron -e proton +e

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

- Conductor 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: A)attractive B)repulsive C)zero D)it depends whether the rod is positive or negative

Coulomb’s Law Point charges exert forces on each other: (Coulomb’s constant) is a unit vector parallel to r

Example 1: Find the magnitude of the force between the charges +10  C and -5  C separated by 20 cm.

Example 2: L L mm qq GIVEN: Identical Masses, m=1.0 gram Equal charges q L= 60 cm FIND: Charge, q (equilibrium)

Quiz: L L m m 2q q/2 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. (equilibrium) ? ?

Finding Resultant force vector: Find: Force (vector) on q 3, in Cartesian form. 400mm 300mm

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