Running late

I may be a few minutes late tonight.  Sorry!

Review

Charge
Electron
Proton
Neutron
Quark
Coulomb's law (inverse square)

Current
Voltage
Resistance
Ohm's law (V = I R)

Circuits
Series
Parallel
Brightness problems (based on current, if bulbs are identical)

Schematic symbols
Light bulbs lighting
Batteries

Magnetism
Electromagnetism
Electromagnetic induction

Motors vs. engines
Basics of 2-stroke engines

Einstein 
Special relativity (time changing between observers)
General relativity (gravity caused by distortions of space caused by mass)

Online tonight

Between 8 and 9 this evening (Tuesday), feel free to email me questions for quick responses. Be safe in the snow.

Seanplally@gmail.com

I'll repeat this at some points before the final.

Why do we still care about Einstein?

Worth a read (from an Einstein scholar and former prof of mine):

http://www.pitt.edu/~jdnorton/Goodies/Einstein_and_S/index.html

Notes from class:

And then there was Einstein…

Albert Einstein 1879-1955

http://www.aip.org/history/einstein/index.html

What’s happening around the turn of the 20th century? Physics was set to explode with 30 brilliant years of excitement and unprecedented activity

X-rays – Roentgen

Radioactivity – Becquerel, Marie & Pierre Curie

Blackbody radiation (and the quantum discontinuity) – Planck

1905/6 – Einstein publishes 6 major papers:

a) “On the electrodynamics of moving bodies”

b) “Does the inertia of a body depend upon its energy content?”

c) “On a heuristic point of view about the creation and conversion of light”

d) “On the theory of the Brownian movement”

e) “On the movement of small particles suspended in stationary liquid demanded by the molecular-kinetic theory of heat”

f) “A new determination of molecular dimensions”

What are these about anyway?

a. Special relativity (SR)

b. E = m c2 (actually, L = m c2)

c. Photoelectric effect, light quanta, fluorescence

d. Same as title

e. Brownian motion agan

f. Avagadro’s number, etc.

Now, these are interesting (and very different fields of study), but is this why we revere Uncle Al? Not necessarily. Others (Poincare, Lorentz) were working on what would become SR. Planck had introduced the quantum discontinuity (E = h f) and quantum mechanics (QM) would have many contributors. The photoelectric effect had also several investigators (Lenard, et.al.).

Mostly, Einstein’s legend grows because of General Relativity (GR), which appears 1912-1915 and later and on which he worked largely alone with pad and pen. He forced us to re-examine how we see ourselves in the universe; indeed, how we think of gravitation. All of this around the time his marriage was falling apart (he married young after fathering 1 illegitimate child) and he began an affair with his cousin (whom he would later marry). Also, between 1902 and 1909, Einstein held a modest post in Bern, Switzerland as a Patent Clerk. By 1914, he would be director of the Kaiser Wilhelm Institute (later Max Planck Institute).

Special Relativity

Spaceship – Inside an inertial reference frame (constant velocity), you can’t tell whether or not you’re moving (“Principle of Relativity”)

Biographical notes

1879 – born in Ulm, Germany

1884 – receives first compass

1895 – attempts to gain entrance to Swiss Polytechnic (and finish high school early), but is rejected

1896 – begins Federal Polytechnic (ETH) in Zurich, Switzerland

1898 – meets Mileva Maric

1900 – graduates from ETH

1901 – Einstein becomes Swiss citizen and moves to Bern; Mileva becomes pregnant

1902 – Lieserl born (put up for adoption); Hermann dies

1903 – Albert and Mileva marry

1904 – Hans Albert born

1905 – Einstein’s “Annus Mirabilus”, his miracle year; Ph.D. (Zurich)

1919 – divorces Mileva (having lived apart for 5 years); marries Elsa; GR verified

1921 – awarded the Nobel Prize in Physics "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect".

1933 – settles in Princeton, NJ

1936 – Elsa dies

1939 – E. writes FDR

1940 – E. becomes American citizen

1949 – Mileva dies

1955 – E. dies

http://www.aip.org/history/einstein/index.html

http://www.albert-einstein.org/

http://einstein.stanford.edu/

http://en.wikipedia.org/wiki/Einstein

General Relativity

By 1907, E. wanted to advance the SR theory to include non-inertial (accelerated) frames of reference. Around this time, E. has the “happiest thought of my life”. In a uniformly accelerated spaceship, a stationary thing (ball, etc.) would appear to be falling (accelerating) down – it would be indistinguishable from normally accelerated motion. Light, too, follows this idea. Two clocks at different ends of an accelerated spaceship would be out of sync. Gravity is the result of the curvature of space and time?

Why does the Earth follow the Sun? Gravity – the very presence of the Sun causes Earth to veer from its otherwise straight (Newtonian inertial) path. With the Sun, it takes an elliptical path as its natural motion. Getting to this point, and showing that mass alters space and time is the real genius.

There is a breakdown of the observed geometry (Euclidean). E. must use non-Euclidean geometry (Gauss, surfaces, infinitesimal geometry) to consider the behavior of things (rods, etc.) on surfaces. He also considers the shortest distance between 2 points on a sphere (geodesic, great circle). He obtains the mathematical advice of his friend Marcel Grossman and studies (at great length) tensor calculus, differential geometry, Riemann and Minkowski math … it’s all puzzle solving. Soon, the principle of equivalence emerges. Eventually, the gravitational field equations appear (to show how matter “produces” gravity. GR was mostly worked out by 1913

Electromagnetic Induction

Generator - a motor in reverse

Magnetism questions

1. In general, what causes magnetism?

2. What is electromagnetism?

3. What is the peculiarity involving magnetic north?

4. How would you find true north?

5. What is a motor and how does it basically work?

6. How do compasses respond to magnetic fields?

7.  What is electromagnetic induction?

8.  What is a generator?

9.  What is a transformer?

10.  Don't forget to review all of the circuit questions from earlier.  Emphasize:

a.  V, I and R -- know what they are, their units, and how to calculate them (V = I R)
b.  the difference between series and parallel circuits -- particularly, how to calculate currents
c.  related to series and parallel circuits -- know how to ascertain relative bulb brightnesses in circuits

11.  Regarding the earliest stuff (for the final exam) on charge.  Focus on:

a.  what the charge concept means
b.  electron, proton, neutron, quark
c.  Coulomb's law (as an inverse square law)

A few more -

12.  Distinguish between motors and generators.

13.  Explain the basic parts of the speaker.

14.  Differentiate between a motor and an engine.

15.  Explain the basic processes of the 2-stroke engine.

Student help

Folks,

I did not mention this in class - sorry!  A couple of students have requested some help with material in the class.  There is not a formal tutoring process in place for this class, nor do I have a TA or some such.  We'll have to do the next best thing - see if we can formalize a study group before the final exam (Monday, December 16 at class time).

After class tonight, all of you interested in forming a study group should stick around - we'll see if we can put something together to help you all.  I will not be involved directly, but I'll help coordinate the endeavor.  Also, if you agree on a night, maybe we could set up a 1 hour "email hour" wherein you ask questions of me directly.  That could work for everyone, actually.

See you tonight.

SL