Chapter 32-1
Inductance
Faradays law
B(t)
d B E ds = dt
E
Lenzs Law
Lenzs law: the induced current in a loop is in the direction that creates a magnetic field (Binduce) that opposes the change in magnetic flux through the area enclosed by the loop B(t) 0
Chapter 31 - 2
Faradays Law
Faradays law Nonconservetive
d B E ds = dt
B(t) E
E ds = 0
Lenzs Law
Lenzs law: the induced current in a loop is in the direction that creates a magnetic field (Binduce) that opposes the change in magnetic flux through the are
Chapter 31 - 2
Faradays Law
Faradays law
B(t)
d B E ds = dt
E
Faradays law something wrong?
d B E ds = dt
E ds = 0
Induced Electric Fields
The induced electric field generated by a changing magnetic field is a nonconservative field is only true in specia
Chapter 31 - 1
Faradays Law
Magnetism
Oersted : An electric current produces a magnetic field
Hans Christian Oersted doing his famous experiment
A Great Question
E
B
E ?
B
Oersted/Ampere/Biot-Savart
Many scientists
Michael Faraday
1791 1867
Faradays Exper
Chapter 30 -3
Sources of the Magnetic Field
Classification of Magnetic Substances
Diamagnetic Ferromagnetic Paramagnetic
Diamagnetism
When an external magnetic field is applied to a diamagnetic substance, a weak magnetic moment is induced in the direction
Chapter 30 -2
Sources of the Magnetic Field
Gauss Law in Magnetism
B dA = 0
Closed surface
Amperes Law
Amperes law states that the line integral of B . ds around any closed path equals oI where I is the total steady current passing through any surface bo
Chapter 30 -2
Sources of the Magnetic Field
Biot-Savart Law
o I ds r dB = 2 4 r
o I B= 4
ds r r2
B Field vs. E Field
o I B= 4 ds r r2
qin E = E dA = o
B = B dA = ?
Magnetic Flux
The magnetic flux associated with a magnetic field is defined in a way simil
Chapter 30 -1
Sources of the Magnetic Field
Magnetic Field of a Wire
A compass can be used to detect the magnetic field When there is no current in the wire, there is no field due to the current The compass needles all point toward the Earths north pole d
Chapter 29 - 3
Magnetic Fields
FB on a Charge Moving in a Magnetic Field
Lorenz force F = qE + qv x B
Moving Charges in a Conductor
F = qE + qv x B -FE
VH
E + + +
+
Moving Charges in a Conductor
F = qE + qv x B
+ + + E
VH
+
-FE -
Hall Effect
Hall Effect
Chapter 29 - 2
Magnetic Fields
Charged Particle in a Magnetic Field
Consider a particle moving in an external magnetic field with its velocity perpendicular to the field The force is always directed toward the center of the circular path The magnetic forc
Chapter 29 - 1
Magnetic Fields
A Brief History of Magnetism
The first definite statement is by Greek philosopher Thales of Miletus (about 585B.C.) who said loadstone (Fe3O4), attracts iron because it has a soul.
A Brief History of Magnetism
In China, the
Chapter 28
Direct Current Circuits
Kirchhoffs Rules
Junction Rule
The sum of the currents entering any junction must equal the sum of the currents leaving that junction
Iin = Iout
Charge conservation!
Kirchhoffs Rules
Loop Rule
The sum of the potential d
Chapter 27 - 2
Current and Resistance
Ohms law
J E Experiments Model
J=E
J = ? (E) J=E
nq 2 = me 1 me = = 2 nq
Analysis
Ohms law
J E
J=E
nq = me
2
1 me = = 2 nq
For copper: n=8.5 x 1028/m3 q=e=1.6 x 10-19 C V = 1.57 x 106 m/s vd = 0.0043 m/s d = 3.9 x 1
Chapter 27 - 1
Current and Resistance
Free Charge in E field
Free charges move from high electrical potential to low electrical potential.
Charge Flow - Electric Current
Assume charges are moving perpendicular to a surface of area A If Q is the amount of
Chapter 32-2
Inductance
Self-Inductance
I
/R
(+L)/R
(+L)/R
t
Inductance
A circuit element that has a large selfinductance is called an inductor
RL Circuit
An RL circuit contains an inductor and a resistor When the switch is closed (at time t = 0), the cu
Chapter 32-3
Inductance
Energy Density
Energy Density of Magnetic Field
U B2 uB = = Al 2 o
Energy Density of Electric Field
uE = o E2
LC Circuit
A capacitor is connected to an inductor Assume the capacitor is initially charged and then the switch is close
D EPARTMENT O F E LECTRONIC AND C OMPUTER E NGINEERING
HONG K ONG UNIVERSITY O F S CIENCE O F T ECHNOLOGY
ELEC 101(L2) BASIC E LECTRONICS
Quiz #1
19:00 - 20:00 16 M arch 2010 LT-B
N ame: S tudent No. :
D~partment
:
Q uestions 1 2 3 4 5 6 T otal
M axi
Chapter 40-42
Introduction to Quantum Physics
1D Schrdinger Equation
U(x)
h 2 d 2 + U = E 2 2m dx
E is the energy of the particle (x) and d/dx must be continuous
Wave Function of a Particle in a Box with Step Potential
qV -q
L/2 The particle can enter the
Chapter 40-42
Introduction to Quantum Physics
1D Schrdinger Equation
U(x)
h 2 d 2 + U = E 2 2m dx
E is the energy of the particle (x) and d/dx must be continuous
Particle in a Box
A particle is confined to a one-dimensional region of space The box is oned
Chapter 40-42
Introduction to Quantum Physics
Classic physics
A particle is described by its position and velocity, a wave is described by its wavelength and frequency.
P =mu
u
f
Newtons laws and Maxwells equations describe their behavior.
Quantum Mechani
Chapter 40-42
Introduction to Quantum Physics
Louis de Broglie
Originally studied history Was awarded the Nobel Prize in 1929
1892 1987 French
Wave Properties of Particles
Louis de Broglie postulated that because photons have both wave and particle charac
Chapter 40-42
Introduction to Quantum Physics
Models of the Atom
Democritus, a fifth century B.C. Greek philosopher, proposed that all matter was composed of indivisible particles called atoms (Greek for uncuttable). Billiard Ball Model (1803)- John Dalto
Chapter 40-42
Introduction to Quantum Physics
Max Planck
Introduced the concept of quantum of action In 1918 he was awarded the Nobel Prize for the discovery of the quantized nature of energy
1858 1947 German
Quantum Revolution
Between 1900 and 1930, anot
Chapter 39
Relativity
Lorentz Transformations
x ' = ( x v t ) t p v t t= t 2= 2x '= tp v c 1
c2 where = 1 v2 1 2 c
Lorentz Velocity Transformation
dx ' u x v = u= ux ux dt ' 1 u xv c2 uy uz ' ' and uz = uy = u xv uzv 1 2 1 2 c c
' x
Momentum
Classic defi
Chapter 39
Relativity
Space
o1
o2
Space
o1 Lp= v tp
o2
Space
Space
L = v t
Length Contraction
Lp= v tp L= v t
t =
t p v 1 2 c
2
= t p
where =
1 v2 1 2 c
Length Contraction
LP v L= = LP 1 2 c
2
Length Contraction
The measured distance between two points de
Chapter 39
Relativity
Triumph of Classic Physics
By the late 19th cent. most of classical physics was complete, and optimistic physicists turned their attention to what they considered minor details in the complete elucidation of their subject.
Galilean R
Chapter 34
Electromagnetic Waves
Solution of Maxwells Equations
E E = oo 2 2 x t
2 2
and
B B = oo 2 2 x t
2 2
The simplest solution to the partial differential equations is a sinusoidal wave:
E = Emax cos (kx t) B = Bmax cos (kx t)
c = / k
c=E
B
PLAY ACTI
Chapter 34
Electromagnetic Waves
Maxwells Equations
rrq E dA = o rr d B E ds = dt rr B dA = 0 rr d E B ds = o I + oo dt
Maxwells Equations in Free Space
rrq 0 E dA = o rr d B E ds = dt rr B dA = 0 rr d E B ds = o I + oo dt
In free space where there is no