/
Static Electricity Electrostatics Static Electricity Electrostatics

Static Electricity Electrostatics - PowerPoint Presentation

natalia-silvester
natalia-silvester . @natalia-silvester
Follow
398 views
Uploaded On 2018-03-21

Static Electricity Electrostatics - PPT Presentation

Examples of electrostatic discharges Lightning static cling in dryers foot dragging shocking cats Electrical charges come in two types and Amber Gk electron is associated with ID: 659877

field charge positive charges charge field charges positive universe negative strength force electric electron analogously parallels units proton distance

Share:

Link:

Embed:

Download Presentation from below link

Download Presentation The PPT/PDF document "Static Electricity Electrostatics" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.


Presentation Transcript

Slide1

Static ElectricitySlide2

Electrostatics

Examples of electrostatic discharges

Lightning

– static cling in dryers

“foot dragging” – “shocking” cats

Electrical charges come in two types, + and –

Amber (Gk. electron) is associated with –

Glass is associated with +

Charging:

By induction

By conduction (conductors and insulators)Slide3

Electrical Charges

Negative (electron)

Positive (proton)

Opposite charges (+ and –) attract whereas like charges (+ and + or – and –) repel

Charge is measured in Coulombs, C

Quantities of charge

Electron = -1.6 x 10

-19

C

Proton = +1.6 x 10

-19

CSlide4

Electric Field

L

ines

Directed

from positive to negative charge

Show the path that a

positive

unit test charge would take. Account for action-at-a-distance forces.Slide5

Electric Field Strength

E

=

F

e

/q by

definition (force per unit charge

)Or Fe

=

E

q

(where

E

= electric field strength)

Units of

E

are N/C

Parallels

W

= m

g

(where

g

=

grav

field strength)Slide6

Coulomb’s Law

First worked out using a torsion balance

Pendulum apparatus easier to understand

F

e

= mg tan(

θ

) found proportional to q1 and q2

F

e

= mg tan

(

θ

)

found inversely proportional to r

2

F

e

= k

e

q

1

q

2

/r

2

where

k

e

= 9 x 10

9

Nm

2

/C

2

Parallels Newton’s universal law of gravitation

F

g

= Gm

1

m

2

/r

2

where G = 6.67 x 10

-11

Nm

2

/kg

2

Note that F

e

/

F

g

= 4.17

x

10

42

; therefore

F

e

>>>>

F

gSlide7

Why Gravity Dominates in Universe

Because

F

e

/

F

g

= 4.17 x 1042 and Fe

>>>>

F

g

, then why does gravity dominate in the universe?

The universe is “neutral” in terms of overall charge; that is, the number of electrons is balanced by the number of protons.

Individual objects are most commonly neutral because they contain roughly equal numbers of positive and negative charges. Slide8

A Couple of Examples

F

e

= k

e

q

1

q2/r2 where

k

e

= 9 x 10

9

Nm

2

/

C

2

Analogously

F

g

= Gm

1

m

2

/r

2

However,

F

g

is only attractive (unless we are talking the grand scale of the universe...

) whereas

F

e

can be either attractive

or repulsive

F

e

=

q

E

Analogously

W

= m

g

This is why

g

is sometimes called the gravitational field strength and is expressed in units of N/kgSlide9

E. C. HW Problems (1/3 pt

ea

)

What is the direction of the field 1 m away from the 1C charge, in or out of the 1C charge?

What force would a 1.4x10

-5

C negative charge experience at 1m distance from the 1C positive charge?

Would the force be directed toward or away from the 1C charge?Slide10

E.C. Homework Note

Because Dr. Wenning will be gone for two weeks, please submit your E.C. homework solutions in hard copy at the start of the next class period.