physics 121: electricity & magnetism – lecture 2 carsten denker njit physics department center...
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![Page 1: Physics 121: Electricity & Magnetism – Lecture 2 Carsten Denker NJIT Physics Department Center for Solar–Terrestrial Research](https://reader036.vdocuments.us/reader036/viewer/2022062308/56649d615503460f94a42754/html5/thumbnails/1.jpg)
Physics 121: Electricity & Magnetism – Lecture 2
Carsten Denker
NJIT Physics DepartmentCenter for Solar–Terrestrial
Research
![Page 2: Physics 121: Electricity & Magnetism – Lecture 2 Carsten Denker NJIT Physics Department Center for Solar–Terrestrial Research](https://reader036.vdocuments.us/reader036/viewer/2022062308/56649d615503460f94a42754/html5/thumbnails/2.jpg)
January 24, 2007 Center for Solar-Terrestrial Research
Introduction
Charges and ForcesElectric FieldElectric Field LinesElectric Field Due to a Point ChargeElectric Field Due to an Electric DipoleElectric Field Due to a Line ChargePoint Charge in an Electric Field Dipole in an Electric Field
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January 24, 2007 Center for Solar-Terrestrial Research
Electric Field
Uranium nucleus: 3 1021 N/C
Electric breakdown in air: 3 106 N/C
Photocopier drum: 105 N/C
Charged comb: 103 N/C Copper wire: 102 N/C
Scalar fields: temperature, pressure, …
Vector fields: electric field, flow field, …
Electric field0
FE
q
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January 24, 2007 Center for Solar-Terrestrial Research
Electric Field Lines
Electric field lines extend away from positive charge (where they originate) and toward negative charge (where they terminate).
Electric Dipole
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January 24, 2007 Center for Solar-Terrestrial Research
Electric Field Due to a Point Charge
Point charge
Superposition principle
02 2
0 0 0
1 1
4 4
q q qFF E
r q r
0 01 02 0
01 02 0
0 0 0
1 2
n
n
n
F F F F
F F FE
q q q
E E E
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January 24, 2007 Center for Solar-Terrestrial Research
Electric Field Due to an Electric Dipole and a Line Charge
Point charge q [C] Line charge
density [C m1] Surface charge
density [C m2] Volume charge
density [C m3]
30
1 and
2
pE p qd
z
3/ 22 204
qzE
z R
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January 24, 2007 Center for Solar-Terrestrial Research
Point Charge in an Electrical Field
The electrostatic force acting on a charged particle located in an external electric field has the direction of if the charge q of the particle is positive and has the opposite direction if q is negative. Ink–jet printer
Millikan experiment
F
E
E
F qE
with 1, 2, 3,q ne n
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January 24, 2007 Center for Solar-Terrestrial Research
Dipole in an Electric Field
Torque
Potential energy
p E
U p E