PHYSICS 1E03

Dr. W. OkońOffice: ABB-150 e-mail: okon@physics.mcmaster.ca

Class: Tue/Thu 9-12 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 – start next Tues. We will automatically replace your lab mark with your old mark if you have done ALL of the labs previously

Homework + Doing Homework + Doing WellWell

Download and print the lecture notes in Power Point format from Download and print the lecture notes in Power Point format from the my web page. Bring the notes for class and add your own the my web page. Bring the notes for class and add your own notes to them during the lecture. notes to them during the lecture. Read Read the textbook, either just the textbook, either just before or just after the lecture, and add to your notes as you before or just after the lecture, and add to your notes as you read. Try to solve all the assignment problems, these are very read. Try to solve all the assignment problems, these are very helpful for the tests!helpful for the tests!

A list of suggested problems from the textbook is posted as a A list of suggested problems from the textbook is posted as a file. You can download and print these. As we cover the file. You can download and print these. As we cover the material from the textbook you can try to do the appropriate material from the textbook you can try to do the appropriate questions from this list if you’re done all the assignments.questions from this list if you’re done all the assignments.

Do NOT work alone, find someone to solve the problems with Do NOT work alone, find someone to solve the problems with and talk about them/physics. For the multiple choice type and talk about them/physics. For the multiple choice type questions, look at the Quick Quizzes in the textbook, and old questions, look at the Quick Quizzes in the textbook, and old tests online.tests online.

PHYSICS 1E03PHYSICS 1E03

I. Electrostatics

II. DC Circuits

III. Magnetism

IV. Waves

IntroductionIntroduction

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?How do things interact?

Electric Charge • A scalar quantity• Comes in “positive” and “negative”

+

+

-

+

-

-

F

REPEL

REPEL

ATTRACT

Units: coulomb, C

and also “smallest unit of charge”, e 1.60210-19 C

F

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: Particle Chargeelectron -eproton +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) attractiveB) repulsiveC) zeroD) it depends whether the

rod is positive or negative

Coulomb’s Law

Point charges exert forces on each other:21 qq ,

r

1q2q

12F

r̂

1 2

12 2ˆ

e

q qF k

r r

2

29109888C

mNxke . (Coulomb’s constant)

r̂ is a unit vector parallel to r

21F

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

Example 2:

L L30 30

m m

q q

GIVEN:•Identical Masses, m=1.0 gram

•Equal charges q

•L= 60 cm FIND: Charge, q

(equilibrium)

Quiz:

LL

m m2q q/2

What happens to each angle ifthe 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 q3 , in Cartesian form.

Cq 101

220q C

Cq 303

400mm

300mm

440q C

solution