Lecture 1 - Jan.8, 2007phys102/ClassNotes/Lecture1...What is charge? • Introduction • First...

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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

DEMO 1

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1

+ + + +

++

++glass

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

Conclude:

DEMO 1

• Introduction

• First Question

History

• What is charge?

• CHARGE

CONVENTION

• DEMO 1

+ + + +

++

++glass

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

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)

Lecture 1 - Jan.8, 2007phys102/ClassNotes/Lecture1...What is charge? • Introduction • First...

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