Phsics Newton's Law
Phsics Newton's Law
Phsics Newton's Law
and
Coulomb’s Law
Electrostatics
2
Force among two electric charges
• Experiments on charged
objects show that
– Charged objects with same
sign repel each other
– Charged objects with
different sign attract each
other
Atom
• In 18th century, it was assumed
that electric charge is some type
of weightless continuous fluid.
• Later on 20th century, Ernest
Rutherford investigated structure
of atom and revealed its
constituents.
-
n + +nn -
++ + n
n +
n
- + n +
n
- -
Neutral Atom
Number of electrons = Number of protons
Electric Forces
F F
+ +
F F +
-
Coulomb’s Law
• Consider two point charges
and placed at distance
apart.
• The two charges exert
force on each other along
the line between them.
• The force is repulsion if the
two charges are the same
sign, the force is attraction
if the two charges are the
opposite sign.
Coulomb’s Law – Gives the electric force
between two point charges.
Inverse Square
Law
F q2 F
q1
r
If r is doubled then F is : ¼ of F
If q1 is doubled then F is : 2F
3μC 3μC
40g 40g
50cm
The electric force is much greater than the
gravitational force
Example 3
- 5μC
45º
20cm
F1 45º
5μC - 4μC
20cm F2
20º
10º 10º
L = 30cm L = 30cm
FE 30sin10º FE
q q
r
r =2(30sin10º)=10.4cm
Coulombs Law
Two Positive Charges
•What is the force between two positive charges each 1 nanoCoulomb
1cm apart in a typical demo? Why is the force so weak here?
q1 q2 1 nC 1 cm 1 nC
r
Repulsion
16
Principle of Superposition
Three charges In a line
• Example of charges in a line
x
1 2 3
– Three charges lie on the x axis: q1=+25 nC at the origin, q2= -12 nC at x
=2m, q3=+18 nC at x=3 m. What is the net force on q1? We simply add the
two forces keeping track of their directions. Let a positive force be one in the
+ x direction.
17
Electric Field Intensity
F K Qq / r2 KQ
E= = =
q q r2
Note that the field strength is independent of the charge placed in it.
F G Mm / r2 GM
g= = = 2
m m r
Again, the field strength is independent of the mass place in it.
Electric field strength
Electric field strength is defined as the force experienced
per unit charge. The charge in the equation refers to the
charge of the particle in the field.
electric field strength = force / charge
E = F/Q
2
Force among two electric charges
• Experiments on charged
objects show that
– Charged objects with same
sign repel each other
– Charged objects with
different sign attract each
other
Atom
• In 18th century, it was assumed
that electric charge is some type
of weightless continuous fluid.
• Later on 20th century, Ernest
Rutherford investigated structure
of atom and revealed its
constituents.
-
n + +nn -
++ + n
n +
n
- + n +
n
- -
Neutral Atom
Number of electrons = Number of protons
Electric Forces
F F
+ +
F F +
-
Coulomb’s Law
• Consider two point charges
and placed at distance
apart.
• The two charges exert
force on each other along
the line between them.
• The force is repulsion if the
two charges are the same
sign, the force is attraction
if the two charges are the
opposite sign.
Coulomb’s Law – Gives the electric force
between two point charges.
Inverse Square
Law
3μC 3μC
40g 40g
50cm
The electric force is much greater than the
gravitational force
Example 2
- 5μC
45º
20cm
F1 45º
5μC - 4μC
20cm F2
x
1 2 3
– Three charges lie on the x axis: q1=+25 nC at the origin, q2= -12 nC at x
=2m, q3=+18 nC at x=3 m. What is the net force on q1? We simply add the
two forces keeping track of their directions. Let a positive force be one in the
+ x direction.
14
Electric Field Intensity
F K Qq / r2 KQ
E= = =
q q r2
Note that the field strength is independent of the charge placed in it.
F G Mm / r2 GM
g= = = 2
m m r
Again, the field strength is independent of the mass place in it.
Electric field strength
Electric field strength is defined as the force experienced
per unit charge. The charge in the equation refers to the
charge of the particle in the field.
electric field strength = force / charge
E = F/Q
Conductors
material that easily conducts electrical current.
The best conductors are single-element material (copper, silver, gold,
aluminum).
One valence electron very loosely bound to the atom- free electron.
Insulators
material does not conduct electric current
valence electron are tightly bound to the atom – less free electron ( like glass,
rubber and porcelain.
1.2 Semiconductors, Conductors and
Insulators
Semiconductors
material between conductors and insulators in its ability to conduct electric
current
in its pure (intrinsic) state is neither a good conductor nor a good insulator
most commonly use semiconductor ; silicon(Si), germanium (Ge), and
carbon(C).
contains four valence electrons
Intrinsic
Semiconductor
Valence
Cell
Covalent bonds
S
i
S S S
i i i
S
i
1.2 Semiconductors, Conductors and
Insulators
Energy Bands
at room temperature
27°
sharing of valence
electron To form Si crystal
produce the
covalent bond
1.3 Covalent Bonding
a free electron
and
its matching
valence
band hole
FIGURE 1-11 Creation of electron-hole pairs in a silicon crystal. Electrons in the
conduction band are free.
1.4 Conduction in Semiconductor
(Conduction Electron and holes)
FIGURE 1-12 Electron-hole pairs in a silicon crystal. Free electrons are being
generated continuously while some recombine with holes.
1.4 Conduction in Semiconductor
(Electron and holes currents)
Electron
current free
electrons
Apply
voltage
B
impurity
atom
Fig.3.2
•Working; A P-N junction diode is a one way device offering low resistance when forward biased and behaving almost as
an insulator when reverse biased. Hence such diodes are mostly used as rectifiers for converting alternating current into
direct current.
1.7.2 Fermi Function–The Probability of an Energy State
Being Occupied by an Electron
Ef is called the Fermi energy or
the Fermi level.
Boltzmann
approximation:
Boltzmann Approximation
Solution: (a)
0.146 eV
Ec Ec
Ef
Ef
0.31
Ev eV Ev
(a) (b
)
Modern Semiconductor Devices for Slide 1-27
Integrated Circuits (C. Hu)
1.8.3 The np Product and the Intrinsic Carrier Concentration
Multiply an
d
Solution:
If ,
and
If ,
and
Slide
Modern Semiconductor Devices for 1-30 Circuits (C. Hu)
Integrated
EXAMPLE: Dopant Compensation
What are n and p in Si with (a) Nd = 6×1016 cm-3 and Na = 2×1016 cm-3
and (b) additional 6×1016 cm-3 of Na?
n = 4×1016
(a) + + + + + + cm.-3. . .
Nd =. .6×1016
cm-3
16
N = 2×10
. . . a. . . . .
-3
(b) Na = 2×1016 + 6×1016 = 8×1016 cm-3 > Nd ...cm
++++++ ....
Nd =. .6×1016
cm-3 16
Na = .8×10
- - - - - --3 . . .
cm . . 16
- - p = 2×10
cm-3
Modern Semiconductor Slide 1-31
Devices for Integrated
1.11 Chapter Summary
■ Total energy is
conserved
Practical Applications
Constant
An Example
Another Example
Yet Another Example
Last Example
Conservation of Mechanical
Energy using a Basketball
Hi I am
Sookram, lets
do the lab
Lab Procedure
1. Place the motion
detector on a flat
surface, like in the
diagram to the right
2. Toss a basketball
above the ultrasonic
sensor
3. The sensor will detect
the position, velocity,
and acceleration of
the ball’s flight
Lab Analysis
*
Periodic Motion
■ Periodic motion is a motion that regularly returns to a given
position after a fixed time interval.
■ A particular type of periodic motion is “simple harmonic
motion,” which arises when the force acting on an object is
proportional to the position of the object about some
equilibrium position.
■ The motion of an object
connected to a spring is a
good example.
*
Restoring Force and the
Spring Mass System
❑ In a, the block is displaced to the right of x = 0.
■ The position is positive.
■ The restoring force is directed to
the left (negative).
❑ In b, the block is at the equilibrium position.
■ x = 0
■ The spring is neither stretched nor
compressed.
■ The force is 0.
❑In c, the block is displaced to the left of x = 0.
■ The position is negative.
■ The restoring force is directed to
the right (positive).
*
Recall Hooke’s Law
■ Hooke’s Law states Fs = −kx
⚪ Fs is the restoring force.
■ It is always directed toward the equilibrium position.
■ Therefore, it is always opposite the displacement from
equilibrium.
⚪ k is the force (spring) constant.
⚪ x is the displacement.
■What
is the restoring force for a surface water
wave?
Differential Equation of Motion
■ Using F = ma for the spring, we have
■ But recall that acceleration is the second derivative of
the position:
*
Analysis Model, Simple Harmonic Motion
■ What are the units of k/m, in ?
*
SHM Graphical
Representation
■ A solution to the differential
equation is
*
Motion Equations for SHM
*
SHM Example 1
■ Initial conditions at t = 0 are
⚪ x (0)= A
⚪ v (0) = 0
■ This means φ = 0
■ The acceleration reaches extremes
of ± ω2A at ± A.
■ The velocity reaches extremes of
± ωA at x = 0.
*
SHM Example 2
■ Initial conditions at t = 0 are
⚪ x (0)= 0
⚪ v (0) = vi
■ This means φ = − π / 2
■ The graph is shifted one-quarter
cycle to the right compared to the
graph of x (0) = A.
*
Consider the Energy of SHM Oscillator
■ The spring force is a conservative force, so in a frictionless
system the energy is constant
■ Kinetic energy, as usual, is
*
Transfer of Energy of SHM
■ The total energy is contant at all times, and is (proportional
to the square of the amplitude)
■ Energy is continuously being transferred between potential energy
stored in the spring, and the kinetic energy of the block.
*
Çengel
Boles Thermodynamics
Thermodynamics
An Engineering
Approach
Third Edition
Yunus A. Çengel
Michael A. Boles
Third Edition
WCB/McGraw-Hill
WCB/McGraw-Hill ©
© The
The McGraw-Hill
McGraw-Hill Companies,
Companies, Inc.,1998
Inc.,1998
Çengel
Boles
CHAPTER
1
Thermodynamics
Basic
Concepts of
Thermodynamics
Third Edition
Third Edition
Çengel
Boles
Thermodynamics
Third Edition
Thermodynamic System
Çengel – quantity of matter or a region of
Boles space chosen for study
Thermodynamics
Boundary
– real or imaginary layer that
separates the system from its
surroundings
Surroundings
– physical space outside the system
boundary
Types of Systems
– Closed
– Open
Third Edition
(Fig. 1-13)
Çengel
Boles
Thermodynamics
Third Edition
Çengel
Boles
Thermodynamics
Third Edition
Çengel
Boles
Thermodynamics
Third Edition
boundary
syst
wor
em
Surr k mas
hea
1 s
Surr t Surr
2 3
Third Edition
E = U + KE + PE
Third Edition
(Fig. 1-19)
Çengel
Boles
Thermodynamics
Third Edition
of the system
Examples: volume, mass, total energy
– Intensive properties - are independent of the size
of the system
Examples: temperature, pressure, color
• Extensive properties per unit mass are intensive properties.
specific volume v = Volume/Mass = V/m
density ρ = Mass/Volume = m/V
Third Edition
Third Edition
Compression Process
Çengel
Boles
Thermodynamics
Third Edition
Quasi-Equilibrium Processes
can apply)
• Work-producing devices deliver the
most work
• Work-consuming devices consume
the least amount of work
Third Edition
1
Process
A
Third Edition
(10-3a)