Transcript PHYS_3342_082511 - The University of Texas at Dallas

PHYS 3342
Physics for Bio Science II
Dr. Phillip C. Anderson
PHYS 3342 Physics for Bio Science II
Fall 2011
– INSTRUCTOR:
– Dr. Phillip C. Anderson 972-883-2875 — Room ESCN2.926
(and WSTC2.716)
email: [email protected]
– OFFICE HOURS:
– Dr. Anderson: TR 9:45 – 11:15 AM and by appointment
– PROBLEM SOLVING SESSION
– TBD
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SCHEDULE FOR MATH/PHYSICS TUTORING THROUGH GEMS IN
FOUNDERS 1.304
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Monday, 1-3pm, 4-7pm
Tuesday, noon to 7pm
Wednesday, 1-3pm, 4-7pm
Thursday, noon to 5pm.
TEXT:
– University Physics (12th edition, if you have an older edition – contact me)
by Young&Freedman
– Make sure that there is a “Student Access Kit” with your book. It allows
you the free access to the homework website through which you will do
your HW. It is important to have. You must register for the homework web
site, www.masteringphysics.com. User ID for this class is
MPANDERSON76241. You will need software called “Flash” to be installed
on your computer.
– Slides will be available on web at www.utdallas.edu/~pca015000. They will
be available to day before the lecture. I would reviewing them before class
and printing them out to take notes on.
GRADING:
Exams (3)
3 Exams (Sep 27, Nov 1) @ 20% each
= 40%
On these exams, you will be allowed to rework the problems (not the
multiple choice)
you got wrong and receive half credit for the correct solution. Must be
turned in the
class period following the return of the exams.
Final Exam (Dec 13 @ 2PM)
= 25%
The final will be comprehensive
Short quizzes
= 10%
The worst two grades will be dropped
Homework
= 25%
90% or greater on the homework will be considered 100%
Grading policy:
96.66 – 100: A+
93.33 – 96.65: A
90 – 93.32: A< 60: F
86.66 – 89.99: B+
83.33 – 86.65: B
80 – 83.32: B-
76.66 – 79.99: C+
73.33 – 76.65: C
70 – 73.32: C-
66.66 – 69.99: D+
63.33 – 66.65: D
60 – 63.32: D-
Extra credit
You will be given an extra credit assignment about halfway though the semester. It will
Homework assignments are assigned approximately every two lectures and
are due in a week. The completion of HW is absolutely necessary. If HW is not
done in time, the score will start to decrease. If you cannot make it in time, you
must contact me in order to discuss your problems.
Reading assignments are indicated during the lecture sessions. It is important
to read the book as it will go into more detail than I can go into in class and
may approach the subject from a different direction. It will also have more
examples that will help you understand the concept.
In-class participation
With your syllabus, you will find 2 pages of “flash cards”. These will be used
in class to find out the level of understanding in the class about the current
topics. I will give an example with multiple choices for the answer and you will
hold up the flash card corresponding to the answer.
Many (most?) of you will be taking the MCAT. I will be “teaching to the MCAT”,
covering all of the subjects that will be on the MCAT
ELECTROSTATICS AND ELECTROMAGNETISM
A. Electrostatics
1. Charges, conductors, charge conservation
2. Insulators
3. Coulomb’s law (F = kq1q2/r2, sign conventions)
4. Electric field
a. field lines
b. field due to charge distribution
5. Potential difference, absolute potential at point in space
6. Equipotential lines
7. Electric dipole
a. definition of dipole
b. behavior in electric field
c. potential due to dipole
8. Electrostatic induction
9. Gauss’s law
B. Magnetism
1. Definition of the magnetic field B
2. Existence and direction of force on charge moving in magnetic field
C. Electromagnetic Radiation (Light)
1. Properties of electromagnetic radiation (general properties only)
a. radiation velocity equals constant c in vacuum
b. radiation consists of oscillating electric and magnetic fields that are mutually
perpendicular to each other and to the propagation direction
2. Classification of electromagnetic spectrum (radio, infrared, UV, X-rays, etc.)
ELECTRONIC CIRCUIT ELEMENTS
A. Circuit Elements
1. Current (I = ΔQ/Δt, sign conventions, units)
2. Battery, electromotive force, voltage
3. Terminal potential, internal resistance of battery
4. Resistance
a. Ohm’s law (I = V/R)
b. resistors in series
c. resistors in parallel
d. resistivity (ρ = RA/L)
5. Capacitance
a. concept of parallel-plate capacitor
b. energy of charged capacitor
c. capacitors in series
d. capacitors in parallel
e. dielectrics
6. Discharge of a capacitor through a resistor
7. Conductivity theory
B. Circuits
1. Power in circuits (P = VI, P = I2R)
C. Alternating Currents and Reactive Circuits
1. Root-mean-square current
2. Root-mean-square voltage
LIGHT AND GEOMETRICAL OPTICS
A. Light (Electromagnetic Radiation)
1. Concept of interference, Young’s double-slit experiment
2. Thin films, diffraction grating, single-slit diffraction
3. Other diffraction phenomena, X-ray diffraction
4. Polarization of light
5. Doppler effect (moving light source or observer)
6. Visual spectrum, color
a. energy
b. lasers
B. Geometrical Optics
1. Reflection from plane surface (angle of incidence equals angle of reflection)
2. Refraction, refractive index n, Snell’s law (n1sin1 = n2sin2)
3. Dispersion (change of index of refraction with wavelength)
4. Conditions for total internal reflection
5. Spherical mirrors
a. mirror curvature, radius, focal length
b. use of formula (1/p) + (1/q) = 1/f with sign conventions
c. real and virtual images
6. Thin lenses
a. converging and diverging lenses, focal length
b. use of formula (1/p) + (1/q) = 1/f with sign conventions
c. real and virtual images
d. lens strength, diopters
e. lens aberration
7. Combination of lenses
8. Ray tracing
9. Optical instruments
We will be studying the laws of electromagnetism from a very
“advantageous” position as an already existing great and
consistent picture – we won’t be deducing these laws but
rather applying them in simple situations.
Remember however that it is a great body of experimental
evidence on the basis of which and to rationalize which this
picture was developed!
Electric and magnetic forces (just as gravity) are fundamental
forces of nature
Electric charge (just as mass) is a fundamental characteristic of
particles
Electric charges (not quite like mass):
• Of two kinds: positive (like protons) and negative (like
electrons). Like charges repel each other; unlike charges
attract
• (Total) charge is conserved (even when particles are
created or annihilated)
• Charge is quantized – exists only in integral multiples of
the fundamental charge e  1.6 1019 Coulomb
Electric charge and structure of matter
Conductors are materials
in which charges can move
freely – will always move
while E is present
Charging by induction
In insulators charges
cannot move freely (but
can be displaced with
respect to each other)
Grounding – charges can flow to the Earth
When you rub a plastic rod with fur, the plastic rod becomes negatively
charged and the fur becomes positively charged. As a consequence of
rubbing the rod with the fur,
A. the rod and fur both gain mass.
B. the rod and fur both lose mass.
C. the rod gains mass and the fur loses mass.
D. the rod loses mass and the fur gains mass.
E. none of the above
Coulomb’s Law
Force produced by “point” charge 1 on “point” charge 2:
F12  ke
q1q2
rˆ
2
r
unit vector
rˆ  r / r  r / | r |
ke 
1
40
 9 109 N  m 2 /C 2
permittivi ty of free space
 0  8.85 10 12 C 2 /N  m 2
Electric forces ARE strong:
m1m2
F

G
Comparing to the gravitational force g
2
r
an electron and proton:
between
Fe
(9 109 )  (1.6 1019 )2
39


2
10
!!!
11
31
27
Fg (6.7 10 )  (9.110 )  (1.7 10 )

Another example: 2 protons, one held at rest, another released
r=2.5 mm
+
At rest
+
Initial acceleration?
a(t)?
Superposition of electric forces
For point charges in vacuum (or in air) – we can add forces as a vector sum
q
q
Find a force acting on one of the charges from
the other three
q
L
q
Electric field and Electric Forces
Electric field E is the force per unit “test” charge: F=q2E
Coulomb’s law is “exact” only in electrostatics! (source charges do not move)
Charge #2
Three point charges lie at the vertices of an
equilateral triangle as shown. All three
charges have the same magnitude, but
Charge #1 is positive (+q) and Charges #2
and #3 are negative (–q).
The net electric force that Charges #2 and
#3 exert on Charge #1 is in
–q
Charge #1
+q
y
–q
x
A. the +x-direction.
B. the –x-direction.
C. the +y-direction.
D. the –y-direction.
E. none of the above
Charge #3