electromagnetism i week 8. contents overview overview coulomb’s law coulomb’s law current...
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Electromagnetism IElectromagnetism I
Week 8Week 8
ContentsContents
OverviewOverview Coulomb’s LawCoulomb’s Law CurrentCurrent VoltageVoltage ResistanceResistance Energy and PowerEnergy and Power ReviewReview
The Four ForcesThe Four Forces
1.1. StrongStrong
2.2. ElectromagneticElectromagnetic
3.3. WeakWeak
4.4. GravityGravity
James Clerk MaxwellJames Clerk Maxwell
First person to First person to fully formulate the fully formulate the classical laws of classical laws of electricity and electricity and magnetism.magnetism.
Maxwell’s Equations ofMaxwell’s Equations ofClassical ElectrodynamicsClassical Electrodynamics
BvEqF
Β
ε
j
t
ΕΒc
t
ΒΕ
ε
ρΕ
0
0
2
0
ElectrostaticsElectrostatics
The study of electric forces when all The study of electric forces when all charges are at rest.charges are at rest.
Every particle has a property called Every particle has a property called chargem. The charge is either chargem. The charge is either positive, or negative, or zero.positive, or negative, or zero.
Charge is always conserved.Charge is always conserved. Measured on Coulombs.Measured on Coulombs.
Coulomb’s LawCoulomb’s Law
F1 = kqQ/rF1 = kqQ/r22
F1 = - F2F1 = - F2
k = 1/4πεk = 1/4πε00
It is “sign It is “sign sensitive”.sensitive”.
Very similar to Very similar to gravitation.gravitation.
+Q
+q
F1
F2
The Electric FieldThe Electric Field
+q -q
Electric Field LinesElectric Field Lines
DefinitionsDefinitions
Current: i = q/tCurrent: i = q/t Voltage: V = E/qVoltage: V = E/q Power: P = q/t = ViPower: P = q/t = Vi Energy: E = Pt = VitEnergy: E = Pt = Vit
CurrentCurrent
I = q/tI = q/t j = I/a = q/atj = I/a = q/at AmperesAmperes
q
t
Current vs. EFCurrent vs. EF
+Q -Q
CurrentCurrent
3A
2A
1A
VoltageVoltage
V = E/qV = E/q Also called electric potentialAlso called electric potential VoltsVolts
VoltageVoltage
3V
3V
3V
ResistanceResistance
R = V/iR = V/i Ohms, Ω.Ohms, Ω.
Energy and PowerEnergy and Power
i = q/ti = q/t V = E/qV = E/q R = V/iR = V/i
E = VitE = Vit P = E/t = ViP = E/t = Vi
Electric CircuitsElectric Circuits
SeriesSeries ParallelParallel
CurrentCurrent
SeriesSeries ParallelParallel
I = I1 = I2 = I3 I = I1 + I2 + I3
VoltageVoltage
SeriesSeries ParallelParallel
V = V1 + V2 + V3 V = V1 = V2 = V3
ResistanceResistance
SeriesSeries
I = I1 = I2 = I3
V = V1 + V2 + V3
V/I = V1/I + V2/I + V3/I
V/I = V1/I1 + V2/I2 + V3/I3
R = R1 + R2 + R3
ParallelParallel
I = I1 + I2 + I3
V = V1 = V2 = V3
I/V = I1/V + I2/V + I3/VI/V = I1/V + I2/V + I3/V
I/V = I1/V1 + I2/V2 + I/V = I1/V1 + I2/V2 + I3/V3I3/V3
1/R = 1/R1 + 1/R2 + 1/R31/R = 1/R1 + 1/R2 + 1/R3
ReviewReview
Coulomb’s LawCoulomb’s Law F = kQq/r2F = kQq/r2
DefinitionsDefinitions i = q/ti = q/t V = E/qV = E/q P = q/t = ViP = q/t = Vi E = Pt = VitE = Pt = Vit
Electric CircuitsElectric Circuits SeriesSeries
I = I1 = I2 = I3I = I1 = I2 = I3
V = V1 + V2 + V3V = V1 + V2 + V3
R = R1 + R2 + R3R = R1 + R2 + R3 ParallelParallel
I = I1 + I2 + I3I = I1 + I2 + I3
V = V1 = V2 = V3V = V1 = V2 = V3
1/R = 1/R1 + 1/R2 + 1/R31/R = 1/R1 + 1/R2 + 1/R3
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MagnetismMagnetism
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