Lecture 1-1PHYS 241 Electricity, Magnetism & Optics

Lecture 1-2

PHYS 241 Electricity & Optics

• Physics Department Home page: http://www.physics.purdue.edu/

• Course Home page: http://www.physics.purdue.edu/phys241/

• CHIP Home page: http://chip.physics.purdue.edu/public/241/fall2019/

• Piazza: https://piazza.com/purdue/fall2019/phys241/home

We do NOT use Blackboard web site at ITaP!

• Room 112 – Lecture Hall

• Room 144 - Undergraduate office

• Room 290 - Help center

• Room 290 - Physics Library

In Charge Overall: Prof. Laura J. Pyrak-Nolte

Office: Room 164, PHYS

Phone: 494-3005

Email: ljpn@purdue.edu

Office Hours: by appointment

Lectures T, Th, 10:30-11:20 am & 11:30-12:20 pm

Prof. Hisao Nakanishi

Office: Room 264, PHYS

Phone: 494-5522

Email: Hisao@purdue.edu

Office Hours: Thurs. 2-3 pm

or by appointment

Questions about grades, grade checks, absences, etc…

Lecture 1-3 http://www.physics.purdue.edu/phys241/

Course

Homepage

Lecture 1-4

PHYS 241 Fall 2019 Schedule

Week: Dates

MONDAY TUESDAY

Reading for

Lectures

WEDNESDAY THURSDAY

Reading for

Lectures

Friday

1: Aug 19-23Lecture

Ch. 21:1-3

Lecture

Ch. 21:4-6

2: Aug 26-30 CHIP HW 1Lecture

Ch. 22:1-2

Lecture

Ch. 22:3

3: Sept 2-6HOLIDAY

Labor Day

Lecture

Ch. 22:4-5 CHIP HW 2 Lecture Ch. 23:1-3

4: Sept 9-13 CHIP HW 3Lecture

Ch. 23:4-5

Lecture

Ch 23:6 & Ch. 24:1-2

5: Sept 16-20 CHIP HW 4Lecture

Ch. 24:3-5

Lecture

Ch. 25:1-3

6: Sept 23-27Exam at 8-10 PM

Elliot Hall of Music

Lecture

Ch. 25:4-5 CHIP HW 5Lecture

Ch. 25:6 Ch 26:1

7: Sept 30 – Oct 4CHIP HW 6

Lecture

Ch. 26:2-4

Lecture

Ch. 27:1-2

8: Oct 7-11HOLIDAY

October Break

HOLIDAY

October BreakCHIP HW 7 No Lecture

9: Oct 14-18 CHIP HW 8Lecture

Ch. 27:3-5

Lecture

Ch. 28:1-3

10: Oct 21-25 CHIP HW 9Lecture

Ch. 28:4-5

Lecture

Ch. 28:6-9

11: Oct 28 - Nov 1Exam at 8-10 PM

Elliot Hall of Music

Lecture

Ch. 29:1,2,5CHIP HW 10 Lecture

Ch. 29:4,6,3

12: Nov 4–8 CHIP HW 11

Lecture

Ch. 30:1-4Lecture

Ch. 31:1-4,6

13: Nov 11-15 CHIP HW 12Lecture

Ch. 31:5,7

Lecture

Ch. 32:1-2

14: Nov 18-22 CHIP HW 13Lecture

Ch. 32:3-4

Lecture

Ch. 33:1-4

15: Nov 25-29 No LectureHOLIDAY

Thanksgiving

HOLIDAY

Thanksgiving

16: Dec 2-6Lecture

Ch. 33:7-8CHIP HW 14

Lecture

Review

17: Dec 9-13Final Exam

WeekFinal Exam Week Final Exam Week Final Exam Week Final Exam Week

Calendar

*Read the assigned

Chapter sections prior to

attending class.

*Homework Due Dates

(Monday or Wednesday

@11:59 pm)

*Note Exam Dates

CHIP Home page: http://chip.physics.purdue.edu/public/241/fall2019/

*Check you schedule for the time and location of your recitation

Lecture 1-5

Syllabus

*Register your I-clicker on CHIP.

*Always bring your I-clicker to class.

*5% of your point total is based on

lecture quizzes.

CHIP: http://chip.physics.purdue.edu/public/241/fall2019/

Lecture 1-7

Syllabus (see posted Syllabus for complete details)

Lecture 1-8

Online Forum

We will use Piazza for class discussions to assist you in getting

help fast and efficiently from your classmates and the teaching

assistants. Rather than emailing questions to the teaching staff,

you are encouraged to post your questions on Piazza:

You can sign up for a Piazza account and enroll in our class page at:

https://piazza.com/purdue/fall2019/phys241/home

EMERGENCY PREPAREDNESS –

A MESSAGE FROM PURDUE

To report an emergency, call 911. To obtain updates regarding an ongoing emergency,

sign up for Purdue Alert text messages, view www.purdue.edu/ea.

There are nearly 300 Emergency Telephones outdoors across campus and in parking

garages that connect directly to the PUPD. If you feel threatened or need help, push the

button and you will be connected immediately.

If we hear a fire alarm during class we will immediately suspend class, evacuate the

building, and go to the Engineering Mall. Do not use the elevator.

If we are notified during class of a Shelter in Place requirement for a tornado warning,

we will suspend class and shelter in [the basement].

If we are notified during class of a Shelter in Place requirement for a hazardous

materials release, or a civil disturbance, including a shooting or other use of weapons, we

will suspend class and shelter in the classroom, LOCKING THE DOORS and turning off

the lights.

Please review the Emergency Preparedness website for additional information.

http://www.purdue.edu/ehps/emergency_preparedness/index.html

Lecture 1-10(Static) Electric Charge

Electric charge is an intrinsic property of the fundamental

particles that every atom is made of, and thus of any object in

nature.

Electric charge states of particles:

• negative (electrons, e.g.)

• positive (protons, etc)

• neutral (neutrons, etc)

The net charge of a system is

the algebraic sum of all the

charges of its constituents.

The net electric charge of a

closed system is conserved in

any physical process. But …

obtain net electric charges

get or lose charged particles

Open System can

Lecture 1-11

Quantization of Charge

• Fundamental unit: elementary charge e

, 1, 2, 3,q ne n= =

• An electron carries a

charge of –e ; a proton

carries a charge of +e

It is typically the

electrons that move

between objects.

19 191.602177 10 1.60 10e C C− −

• Coulomb (C): one coulomb is the amount of charge

that is transferred through the cross section of a wire

in 1 second when there is a current of 1 ampere in the

wire.

• Electron charge -e is now defined (as of May, 2019):

e ≡ 1.602176634 x 10-19 C exactly

This defines the unit Coulomb (C)

Lecture 1-12

Charge Conservation and Transfers

• Charge can be transferred from one

object to another.

• Individual charges can also, in fact, be

“destroyed” or “created”, but not net charges

++ +− ee(→ annihilation)

( pair production)

For instance, friction can cause electrons

(or ions) to move from one object to

another.

2

4

2 2

4 2

( ) 2 ( ) ( )

( ) ( )

Zn s H aq SO aq

Zn SO aq H g

+ −

+ −

+ +

→ + +

Lecture 1-13

Conductor vs. Insulator

• Conductors: material in which electric charges can

move around “freely”

– Metals, tap water, human body, …

• Insulators: material in which electric charges are

“frozen” in place

– Air, glass, plastic, …

• Semi-conductor: material in which electric charges

can move around but not as freely as in conductors

– Silicon, germanium, …

Cu 1029 / m3

Ge 1019 / m3

• Super-conductor: material in which charges move

with no resistance at all

− Metals at low (liquid He) temperatures, certain ceramics

at liquid Nitrogen temperatures

Lecture 1-14Observing Electric Charge

• Electric charges exert forces on one another, i.e., they interact.

Like charges repel while unlike charges attract each other.

→ 2 kinds of charges (+, −)

Lecture 1-15

Charging Conductors by induction

grounding

polarization

by induction

Lecture 1-16

Interaction of Charges: Neutral Insulators

+ Polarization of

atoms by induction

Lecture 1-17 Coulomb’s Law

• Charges with the same sign repel each other, and charges

with opposite signs attract each other.

• The magnitude of the electrostatic force between two

particles is proportional to the amount of electric charge

that each possesses and is inversely proportional to the

distance between the two squared.

1 21,2 1,22

1,2

ˆq q

F k rr

= q1 q2

r1,2

1,2r→by 1

on 2

• Coulomb constant:

9 2 2

0

18.99 10 /

4k N m C

=

where 0

is called the permittivity constant.

12 2 1 28.85 10 C N m− − −

2,1F1,2F

Assuming q1, q2

of the same sign

Lecture 1-18How Strong is the Coulomb Force?

Duodecillion

(US notation)

Lecture 1-20

Principle of Superposition

1 21 31 41F F F F= + + +

q1

q2

q3F13

F12

F1

• Add by components or

• Magnitude and direction

separately by using

trigonometry

• Symmetry can help!

Lecture 1-21Principle of Superposition Example

• When several point charges are put together, the total force on

any one charge is the vector sum of the each of the separate

forces acting on that charge.

F = F21y + F31y = 2F21y

F = 2 kQ1Q2

r2cos 300

F =

2 9 109 N m2

C 2 (10−6C)2 0.866

1m( )2

F = 15.59 10−3 N

F

F21

• Exercise:

Q2

Determine force on Q1

Q1=Q2=Q3=1CQ3

R=1m

600

Q1

y

xDetermine force on Q1

F31