UNIT-1 Coulombs Law

8/10/2019 UNIT-1 Coulombs Law

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BY

S Naga Kishore BhavanamB.Tech.,M.B.A- HRM, M.Tech-VLSI, (Ph.D)

Assistant Professor

University College of Engineering & TechnologyAcharya Nagarjuna University

GunturHellow: +91-99895 41444

Email: [email protected]

Coulombs Law


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Electrostaticsis the branch of

electromagnetics dealing with the

effects of electric charges at rest. The fundamental law of electrostatics

is Coulombs law.

Electrostatics


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Electrification by Friction

Electric charge, or `electricity', can

come from batteries and generators.

But some materials become charged

when they are rubbed. Their chargeis sometimes called electrostatic

charge or `static electricity'. It

causes sparks and crackles when you

take off a pullover, and if you slide

out of a car seat and touch the door,

it may even give you a shock.


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Same charges REPEL

+ +

Opposite charges ATTRACT

+-

Electrostatic Force


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Coulombs lawis the law of actionbetween charged bodies.

Coulombs lawgives the electric force

between two po int charges

in anotherwise empty universe.

A point chargeis a charge that occupies a

region of space which is negligibly smallcompared to the distance between the

point charge and any other object.

Coulombs Law


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q1 q2r

2

21

rqkqFe

Electrostatic Force

Amount of force depends on:

CHARGE ON EACH OBJECT DISTANCE BETWEEN OBJECTS

ELECTROSTATIC CONSTANT: k = 8.99 x 109Nm2/C2

Fe

r


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2

21

r

qkqFe 2

21

r

mGmFg

Electrostatic vs. Gravitational Force

Consider two electrons that are 1.0 micrometer apart.

GravitationallyATTRACTED Electrostatically REPELLED

e- e-

r = 1.0 m

Fe Fe

Fg Fg

26

1919229

)101(

)1060.1)(1060.1)(/1099.8(

mx

CxCxCmNx

26

31312211

)101(

)1011.9)(1011.9)(/1067.6(

mx

kgxkgxkgmNx

5.54 x 10-59 N 2.30 x 10-16 N


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Coulombs Law

2

120

21

12

4

12

r

QQaF R

Q1Q212

r

12

F

Force due to Q1

acting on Q2

Unit vector in

direction of R12


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The force on Q1due to Q2is equal in

magnitude but opposite in direction to the

force on Q2due to Q1.

1221 FF

Coulombs Law


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Determine the electrostatic force between an

object with a +2.0 coulomb charge and an object

with a -2.0 coulomb charge if they are separated by

2.0 meters.

Example #1

221

rqkqFe

2

229

)2(

)2)(2)(/1099.8(

m

CCCmNxFe

NxFe91099.8

ATTRACTIVE


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Determine the electrostatic force between an

object with -2.0 micro-coulombs of charge and an

object with -5.0 micro-coulombs of charge if they

are separated by 5.0 nanometers.

Example #2

221

rqkqFe

29

66229

)100.5(

)100.5)(100.2)(/1099.8(

mx

CxCxCmNxFe

NxFe15106.3

REPULSIVE


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Coulombs Law: problem2 Charges

A positive charge of 6.0 x 10 -6C is 0.030m from a second positive

charge of 3.0 x 10 -6C. Calculate the force between the charges.

Fe= k q1 q2

r2

= (8.99 x 109 N m2/C2) (6.0 x 10 -6C) (3.0 x 10 -6C)

( 0.030m )2

=(8.99 x 109 N m2/C2) (18.0 x 10 -12C)

(9.0 x 10 -4 m2)

= + 1.8 x 10 -8N


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Electric Field Intensity

Electric Field Intensity

or

Electric field strength (E)

The force per unit charge when placed in an

electric field

E= F/QIt is measured in newtons/coulomb


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Thank YOU

UNIT-1 Coulombs Law

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