PHYS 3342Physics for Bio Science II

Dr. Phillip C. Anderson

PHYS 3342 Physics for Bio Science IIFall 2011

– INSTRUCTOR:– Dr. Phillip C. Anderson 972-883-2875 — Room ESCN2.926

(and WSTC2.716) email: phillip.anderson1@utdallas.edu

– OFFICE HOURS:– Dr. Anderson: TR 9:45 – 11:15 AM and by appointment

– PROBLEM SOLVING SESSION– TBD

- SCHEDULE FOR MATH/PHYSICS TUTORING THROUGH GEMS IN FOUNDERS 1.304– 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 theclass 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+ 86.66 – 89.99: B+ 76.66 – 79.99: C+ 66.66 – 69.99: D+93.33 – 96.65: A 83.33 – 86.65: B 73.33 – 76.65: C 63.33 – 66.65: D90 – 93.32: A- 80 – 83.32: B- 70 – 73.32: C- 60 – 63.32: D-< 60: F

Extra credit You will be given an extra credit assignment about halfway though the semester. It will

consist of 20 homework problems. You will receive ½ point added to your final grade for each problem worked correctly

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 Coulomb106.1 19−×=e

Electric charge and structure of matter

Charging by induction

Grounding – charges can flow to the Earth

Conductors are materials in which charges can move freely – will always move while E is present

In insulators charges cannot move freely (but can be displaced with respect to each other)

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:

22120

229

0

m/NC1085.8

space free ofty permittivi

/CmN1094

1

⋅×=

⋅×==

−ε

πεek

rF ˆ2

2112 r

qqke=

unit vector ||//ˆ rrrr == r

Electric forces ARE strong:

Comparing to the gravitational force between an electron and proton:

221

r

mmGFg

€

Fe

Fg

=(9 ×109) ⋅(1.6 ×10−19)2

(6.7 ×10−11) ⋅(9.1×10−31) ⋅(1.7 ×10−27)≈ 2 ×1039 !!!

Another example: 2 protons, one held at rest, another released

+ +

At rest

r=2.5 mm Initial acceleration?a(t)?

Superposition of electric forces

For point charges in vacuum (or in air) – we can add forces as a vector sum

L

q q

q q

Find a force acting on one of the charges fromthe other three

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)

Electric field and Electric Forces

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

A. the +x-direction. B. the –x-direction.

C. the +y-direction. D. the –y-direction.

E. none of the above

Charge #1

Charge #2

Charge #3

+q

–q

–q

x

y