Lecture 1 - Jan.8, 2007phys102/ClassNotes/Lecture1...What is charge? • Introduction • First Question History • What is charge? • CHARGE CONVENTION • DEMO 1 • Properties

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PHYS102 Introduction and Charge – slide 1

PHYS102 - Introduction and Charge

Dr. CorcoranDr. Suess

January 8, 2007

\protect \protect \protect \edef OT1OT1\let \enc@update \relax \protect \edef phvphv\protect \edef mm\protect \edef nn\protect \xdef \OT1/phv/m/n/8 \OT1/phv/m/n/8 \OT1/phv/m/n/8 \size@update \enc@update \ignorespaces \relax \protect \relax \protect \edef phvcmtt\protect \xdef \OT1/phv/m/n/8 \OT1/phv/m/n/8 \OT1/phv/m/n/8 \size@update \enc@update http://www.owlnet.rice.edu/~phys102

Introduction

• Introduction

• First Question

History


• Welcome to PHYS102.

Lab preference sheets need to be submitted to Dr.Dodds’s office (HZ Room 109). (There is a box on hisfile cabinet.)

• Important Changes from PHYS101:

The pledged problems are now worth 20% of your finalgrade (vs. 15%)

The final exam is worth 20% of your final grade (vs.25%)


First Question

• Introduction

• First Question

History


Your first question:


First Question

• Introduction

• First Question

History



• Why are you taking this course?


First Question

• Introduction

• First Question

History




to form a deeper understanding of the world aroundme.


First Question

• Introduction

• First Question

History




to form a deeper understanding of the world aroundme.(Only in the ideal case.)


First Question

• Introduction

• First Question

History





to understand how my new cell-phone works.


First Question

• Introduction

• First Question

History






I really like listening to lectures on physics, and Icouldn’t wait to get back to pledged problems.


First Question

• Introduction

• First Question

History







I have to (it’s required of my major).


First Question

• Introduction

• First Question

History







I have to (it’s required of my major).


History

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1

• Properties of charge

• Properties of chargeII• Fundamental unit ofcharge

• Objects and charge



What is charge?

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1





When you think of charge, what comes to mind?


What is charge?

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1






• Positive and negative charges.


What is charge?

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1






• Positive and negative charges.(protons and electrons)


What is charge?

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1







How is charge defined?


What is charge?

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1







How is charge defined? Are you sure they exist?


What is charge?

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1







How is charge defined? Are you sure they exist? If so,how are you sure?


What is charge?

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








The answer to the numerous questions:


What is charge?

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1









Our understanding of charge comes throughexperiments and conventions.


What is charge?

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1









Our understanding of charge comes throughexperiments and conventions.

Charge is an intrisic property of matter (just like mass).


CHARGE CONVENTION

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1





• We currently live by Benjamin Franklin’s convention.


CHARGE CONVENTION

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1





• We currently live by Benjamin Franklin’s convention.


DEMO 1

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1






DEMO 1

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1





Rubbing glass (an insulator or dielectric) rod with silk, we notethat the rod “acquired” a charge (positive) which means thatthe silk has a net negative charge.


DEMO 1

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1






• Based on the demonstration:


DEMO 1

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1







insulatorrubberglass

+ + + +

++

++glass

F

F


DEMO 1

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








+ + + +

++

++glass

F

F

There is something causing the objects to repel orattract.


DEMO 1

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








+ + + +

++

++glass

F

F


Conclude:


DEMO 1

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








+ + + +

++

++glass

F

F


Conclude:

Charges of the same sign repel one another,


DEMO 1

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








+ + + +

++

++glass

F

F


Conclude:

Charges of the same sign repel one another,

and charges of the opposite sign attract one another.


Properties of charge

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1





• Charges of the same sign - repel each other.



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1






• Charges of differing sign - attract each other.



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1







• Charge is conserved.



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








Since this is physics, we need to quantify (or try to quantify)what we see.



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1









We need to begin our analysis of the attraction or repulsion byquantifying charge.



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1









We need to begin our analysis of the attraction or repulsion byquantifying charge.We will usually represent net electric charge by the letter q orQ.



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1









We need to begin our analysis of the attraction or repulsion byquantifying charge.We will usually represent net electric charge by the letter q orQ.NOTE: Charge is treated as a scalar (only a number nodirection).


Properties of charge II

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1





S.I. unit of charge = 1 C “Coulomb”



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1






1 C of charge is extremely large and typical amounts of chargeare pC, nC, µC:



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1







(pC) pico C = 1 × 10−12 C



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1







(pC) pico C = 1 × 10−12 C(nC) nano C = 1 × 10−9 C



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1







(pC) pico C = 1 × 10−12 C(nC) nano C = 1 × 10−9 C

(µC) micro C = 1 × 10−6 C



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1







(pC) pico C = 1 × 10−12 C(nC) nano C = 1 × 10−9 C(µC) micro C = 1 × 10−6 C

When rubbing two objects like silk and glass together, we saycharge transfers from one object to the other.



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








When rubbing two objects like silk and glass together, we saycharge transfers from one object to the other.What do we mean by this?



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








When rubbing two objects like silk and glass together, we saycharge transfers from one object to the other.What do we mean by this?Does charge “flow” like a liquid?



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








When rubbing two objects like silk and glass together, we saycharge transfers from one object to the other.What do we mean by this?Does charge “flow” like a liquid? or does it “flow” in tiny pieces?



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








When rubbing two objects like silk and glass together, we saycharge transfers from one object to the other.What do we mean by this?Does charge “flow” like a liquid? or does it “flow” in tiny pieces?

• Experiments show that charge is made up of integermultiples of a fundamental unit of charge.


Fundamental unit of charge

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1





Fundamental unit of charge = e = 1.602 × 10−19 C.



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1






NOTE: The charge of a single electron is -e and the charge ofa single proton is e.



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1







When any physical quantity exists in discrete amounts ratherthan in continuous amounts, it is said to be “quantized”.



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








If number of electrons transferred from the glass to the silk isne, then the silk acquires ne “spare” electrons while an equalamount of non-neutralized (+) charges remain in the glass:



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1









∴ n+(rod) = ne(silk)



• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1









∴ n+(rod) = ne(silk)⇒ Total charge on silk is given by qsilk = −ne e


Objects and charge

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1





• Most objects around us have zero net charge. (Objectcontains equal number of positive and negative charges.)


Objects and charge

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1






• Materials can be classified into four main classes(depending on how electrons can move through thematerial)


Objects and charge

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1







Conductors - electrons can move almost freely throughthese materials (examples include metals).


Objects and charge

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1








Superconductors - electrons can move without anyinhibitions through these materials (examples includemetals or ceramics cooled to very low temperatures).


Objects and charge

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1









Insulators - electrons can not travel easily through thesematerials (examples include rubber, glass, andplastics).


Objects and charge

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1









Insulators - electrons can not travel easily through thesematerials (examples include rubber, glass, andplastics).

Semiconductors - (an example is silicon)


Documents

Lecture 1 - Jan.8, 2007phys102/ClassNotes/Lecture1...What is charge? • Introduction • First Question History • What is charge? • CHARGE CONVENTION • DEMO 1 • Properties