Programming environments
Programmingenvironments
JavaME
SunSPOTs
Gamedevelopment
O
Operatingsystems
ti
t
Mobilecomputing
Mobileuserinterfaces
Markuplanguages,mobilesecurity,mobileIP
p g g ,
y,
Mobile services
Mobileservices
B2BandB2Cservices
Location
PHYS2213Physics2EE
EdmundTse2007
Forapermanentmagnet,i=0,andH1L+H2l=0,so H iron=
H gap l
Bl
=
L
0 L
Magneticrecording
3headserase,write,read.
Readingthechangingfieldinthetapeinducesasignalinthecoil
Writingtimevariationinthewriteheadistranslatedtoaspacevar
Equivalent Circuits
Rth =
Rth -
VOC
Vth
=
ISC
IN
Thevenin resistance
to calculate this, short all voltage sources, open all current sources,
calculate resultant resistance
VOC = Vth =open
ISC = IN =short
circuit voltage (supply voltage in Thevenin circ
Inverting Conguration
The non-inverting (+) terminal is held at
0V ,
because that's the voltage of
the inverting () terminal.
This means that the 2 resistors behave like a normal voltage divider. However
you know the voltage at one end, and in the middle,
Edmund Li
D IPOLES
When two equal but opposite charges are separated by a short distance, a dipole is formed. Typical
examples of dipoles include transmission lines which are a parallel set of conductors. In this section,
we are interested in determining
Edmund Li
ELECTROMAGNETISM
Electromagnetics is the study of the effects of electric charges at rest and in motion resulting in an
electromagnetic field.
E LECTROMAGNETIC M ODEL
The electromagnetic model is based on several facts:
The electric charge of on
= arg(v) arg(i) = Arg (z)
power f actor = cos() =
P
|S|
Complex Power S
Measured in VA
Total power available
S = v = |Vrms | |Irms |
i
= P + jQ
Where
v
and
i
are complex numbers
P
= True (real) power
Q
= Reactive (imaginary) power
Apparent Power - |S|
Edmund Li
N ULL I DENTITIES
1.
The curl of the gradient of any scalar field is identically zero:
Conversely, if a vector field is curl free, then it can be expressed as the gradient of a scalar field.
For example, if
then we can define a scalar field V su
Edmund Li
V ECTOR A NALYSIS
A vector is a quantitiy with a magnitude and direction which can be expressed as a combination of n
components or coordinates:
. The norm (magnitude, length) of a vector
is the
scalar:
With the properties of:
1.
2.
3.
By using
Edmund Li
STATIC ELECTRIC FIELDS
In electrostatics, electric charges are at rest, and electric fields to not change with time; as such
there are no magnetic fields nor currents. Electrostatics is an important phenomena seen in
lightning, corona, oscillosc
Denition
L=
L=inductance
N =number
N 2 A
l
(H)
of turns in inductor
=permeability
of core
= 0 r
l=length
A=cross
sectional area
Formula
To remember this, take the equivalent formula for capacitors, swap C with L,
and swap i and v.
v=L
di
dt
Energy
E