|1.||Monday, Mar. 6 - Chapter 21 - Electric Charge|
Video 1 - "Electrostatics - Interaction of
Charge", Video 2 - "Distribution of
Charge on a Conductor",
Video 3 - "Induction of Charge".
Design and operation of an electroscope.
Nine basic experimental results:
|2.||Wednesday, Mar. 8|
Discuss the Triboelectric
Series - shows how strongly various materials hang on to their
electrons when you rub them together. Comes from the Web site - How
List the items from Monday plus a few others, in order from most positive to most negative:
Coulomb's Law - what you use to calculate
the force between pairs of charges
|3.||Friday, Mar. 10|
Computer - EM Field program - 3D
sources (Start, Physics, EM Fields) - also
available on the computers in 204 and 121
|4.||Monday, Mar. 13|
E on the axis of a charged disk (Eq. 22-26)
Motion of a charged particle in a uniform electric field
Useful applications: oscilloscope, TV, computer monitor, ink jet printing (p. 592)
Video 6. "Corona Discharge: Detection of Electric Wind".
Video 7. "Momentum of an Electron: Motion Imparted During Collision".
Dipole in an electric field - resulting torque. Potential energy of a dipole
Chapter 23. Gauss' Law --
electric flux, F
= E A cos q
= ... (integral of E dot dA)
|5.||Wednesday, Mar. 15|
Gauss' law: For any closed surface, electric flux
= Fc =
the total enclosed charge
Computer - EM Field - 2D Charged Rods (with Gauss' Law)
Applications of Gauss' Law:
1. Insulating sphere of radius a and total charge Q. E = kQ/r2 (outside), E = (kQ/a3)r (inside)
2. Thin spherical shell with total charge Q. E = kQ/r2 (outside), E = 0 (inside)
3. Infinite line of charge of linear charge density l. E = 2kl / r.
Computer - EM Field - Options, Display Gauss' Law.
4. Nonconducting, infinite plane sheet with surface charge density s. E = s/2e0 (indep. of r)
5. Conducting surface with surface charge density s. E = s/e0 (indep. of r)
|6.||Friday, Mar. 17|
Chapter 24. Electric Potential.
Analogy: gravitational field --- electric field
Definition of potential difference, DV = DU/qo = ..., E = - grad (V)
units: 1 volt = 1 joule/C, electric field: 1 N/C = 1 V/m
Electric potential of a point charge q: V = kq/r
Video 8. "Electromagnetic Shielding". Video 9. "Electricity Demonstrations".
Video 10. "Electrostatics - Part I". Bill Nye the Science Guy.
|7.||Monday, Mar. 20|
Applications of Electrostatics
Xerography - invented by Chester F. Carlson in 1937. How Photocopiers Work - How Laser Printers Work
Night lightning on Jupiter - cloud tops illuminated by sunlight reflected from the moon Io - photos taken by the spacecraft Galileo in October, 1997.
Van de Graaff generator - transparency - Demo: stack of aluminum plates, etc.
Plasma globe - A partially evacuated glass sphere containing a mixture of inert gases. When turned on, these gases become a plasma - a mixture of free electrons and bare atomic nuclei. The smaller glass sphere at the center contains a power source similar to a Tesla coil. It supplies and alternating, high voltage, high frequency, yet small current to the inner sphere. - Demo: touch it, bring a neon tube near to it, look at the light though a diffraction grating
Potential difference - DV = DU/qo = - Ed, symbol for ground, equipotential surfaces
Video 11. "Electrostatics - Part II". Bill Nye the Science Guy.
|8.||Wednesday, Mar. 22|
Computer - EM Field - equipotential lines
Recall: DU = q DV
Definition: 1 electron volt (eV) = 1.60 x 10-19 J (energy conversion factor)
Corona discharge - discharge of a conductor at a high potential into the air producing a visible glow or spark
Demo - induction coil
Chapter 25. Capacitance
|9.||Friday, Mar. 24|
Derivation for a spherical capacitor
Capacitors with dielectrics, C = ke0A/d = kC0, k = the dielectric constant
Fig. 25-15 - Molecules with a permanent electric dipole moment. (a) no external E, (b) E applied
Fig. 25-16 - A non-polar dielectric slab. (a) dielectric slab, (b) apply E0, (c) net electric field E is smaller
so V is smaller and C increases with a dielectric present
Demo - large aluminum capacitor with (a) air, (b) bakelite, (c) cardboard
Video 13. "Parallel Plate Capacitor".
Show and discuss a variety of kinds of capacitors
Capacitors in parallel and series
Flash attachment - energy stored in the capacitor C1 is quickly dissipated via ionization of the xenon gas
and subsequent emission of light. Flash duration = 0.4 ms, cycle time = 0.3 s.
|10.||Monday, Mar. 27|
Energy stored in capacitors = U = ½ CV2
Add a dielectric: U = U0/k
High speed photography - independent study at Augustana in 1996 by Christopher Boldt
and Scott Nowicki - apple - egg - water balloon
Demo - 13 J in five capacitors - boom !
Video 14: "Energy Stored in a Capacitor".
Chapter 26. Current and Resistance
Carbon/zinc battery - electrolyte - sulfuric acid
emf (electromotive force) - a source of emf is any device that will transform non-electrical energy into electrical energy.
e.g. battery, electric generator, solar cell
Video 15: "Operation of a Battery".
Definition of current: i = dq/dt. unit for current: ampere (A). 1 A = 1 C/s
Analogy: water pipe system with a pump, electric circuit with a battery.
Definition - the direction of conventional current flow is opposite to the direction the electrons flow
Drift velocity - it is extremely slow - typically about 1 m/h for i = 10 A
Two forms of Georg Ohm's Law: J = sE, V = i R
Resistivity r of a wire of length l, cross-sectional area A and resistance R, R = rl / A.
Variation or resistivity with temperature, demo: heat a resistor, meas. R with the 4-digit DMM, it decreases slightly; immerse resistor in liquid nitrogen - R increases slightly.
|11.||Friday, Mar. 31|
16: "Temperature and Resistance".
color codes for resistors Remember the color codes with this sentence:
Joule's Law for resistors: P
= i2R =
Vi = V2/R
|12.||Monday, Apr. 3|
Kirchhoff's First (junction) Rule: The algebraic
sum of the currents at any junction in a circuit is zero.
Kirchhoff's Second (loop) Rule: The algebraic sum of the changes in potential around any closed path in a circuit is zero.
Potential difference in a circuit - resistors, batteries
Demo: 6V battery, (variable) resistance box, two DMM's, wires - measure E and i, calculate R
Demo: Add a second resistance box. Results: spreadsheet with graph
Example of using Kirchhoff's rules - two batteries, 7 resistors
Internal battery resistance (ranges from 0.05 ohms for new batteries to 100 ohms for old ones)
Resistors in series: Rs = R1 + R2 + R3
Resistors in parallel: 1/Rp = 1/R1 + 1/R2 + 1/R3
Demo: Three resistors (33 ohm, 56 ohm and 100 ohm) placed in series and then parallel - measure R
|Discussion, Tuesday, Apr. 4|
Example of using Kirchhoff's rules - 3 equations in 3 unknowns
|13.||Wednesday, Apr. 5 - went over Test 1|
18: "Series and Parallel Circuits"
This video (done by high school physics teacher and author Paul Hewitt) uses
a 12 volt automobile battery. It shows what happens when several
standard automobile bulbs are placed in series and then in parallel.
Combining emfs in series and in parallel, typical flashlight:
two D cells (each 1.5 V) in series, small 9 V battery: six internal
1.5 V cells in series, 12 V automobile battery: six 2.0 V cells in
series but each cell has several dozen smaller 2 V cells in
parallel (currents up to 50 A).
|14.||Monday, Apr. 10|
Chapter 28 - Magnetic Fields
Compare fields: gravitational, electric, magnetic
Magnetic fields of a bar magnet, a powerful neodymium (disk) magnet, and a horseshoe magnet, applet
Demo - magnets and zinc coated iron filings on overhead, explore with the Magneprobe
Earth's magnetic field, Demo - ball (Earth) containing a magnet
Video 19: "Mapping Magnetic Field Lines"
Magnetic declination = direction of true north = 2 degrees east of north at Augustana
direction of magnetic north using a compass map
Dip needle to show the inclination - here in the Quad Cities we are currently at about 55 degrees
Magnetic force on a moving charge, Fm = q v x B
Magnitude of Fm = qvB sin q, direction of Fm is perpendicular to the plane containing v and B.
Memory devices: 1. three-finger rule. 2. alternate right-hand rule.
Video 20: "Forces on an Electron Beam"
Demo: show the corresponding apparatus
Two special cases: 1. v parallel or antiparallel to B: Fm = 0. 2. v perpendicular to B: Fm = qvB.
Circular orbits in a uniform magnetic field, centripetal force = magnetic force,
r = mv/qB, cyclotron frequency = w = qB/m.
Example: the Tevatron at Fermilab
v not parallel to B: spiral path. Occurs in nature around B (Earth) - produces the northern lights (aurora borealis) Interplanetary magnetic field
Photos of Nov. 5, 2001. For the latest information on solar activity go to SpaceWeather.com.
Here is their spectacular aurora gallery for Nov. 5-6, 2001.
|15.||Wednesday, Apr. 12|
Force on a current segment in a magnetic
field, magnitude of the force = Fm = i L B sin
Hall effect. Hall voltage = V = vd B l. demo: digital Tesla meter (to measure magnetic field)
Galvanometer - add a coil spring. Fig. 28-22. NiAB = k f where k = torsional constant
General form for a current loop: torque vector = t = i A x B = m x B, m = i A = magnetic moment.
Chapter 29. Magnetic Fields Due to Currents
|16.||Tuesday, Apr. 18 (regular class at 10:00 am)|
Two parallel current carrying wires
Video 21: "Forces on a Current Carrying Wire"
Demo: current balance apparatus used in lab
Magnetic field around a single current loop
Ampere's Law - For any closed path around a one or more wires carrying a current,
line integral ( B . ds ) = m0 ienc. The integration loop is called an Amperian loop.
Computer: EMField - explain Ampere's Law, file: isheets.emf
Magnetic field inside a solenoid: B = m0 n i (n = no. of turns per meter)
Demo: solenoid, measure B with the digital Tesla meter
Toroid - computer: EMfield - file: coaxmag.emf
|17.||Wednesday, Apr. 19|
- magnetic field around a single current loop
Current loop as a magnetic dipole, m = i A.
Chapter 30. Induction and Inductance
|18.||Friday, Apr. 21|
Demo: Drop strong, small neodymium magnets into three tubes (PVC, aluminum,
copper), time the fall, reverse the magnet.
Heliflux magnetometer - gift of Erick Schonstedt
Motional emf, induced current in a circuit, E = B L v
Applications: recording and playback heads in tape recorders, VCRs, floppy disks, hard disks, electric guitars
Electric generator (dynamo), motor - electrical to mechanical, generator - mechanical to electrical
ac generator (Fig. 31-6, p. 836): E = N B A w sin (wt), w = the angular frequency (in rad/s)
applet w = 2 p f, f = freq. in Hz
|19.||Wednesday, Apr. 26|
generator #1 - incandescent bulb, flicker bulb
Demo: generator #2 - (a) nothing - turns easily, (b) flashlight bulb, (c) a wire near a compass, (d) wrap the wire around the compass, what if there were several turns? (e) thermoelectric heat pump - Peltier (pelt-ee-yay) effect - turn crank one way (hot) and then the other (cold). This is how the Coleman thermoelectric heat pump works.
How does a loudspeaker work?
Ring launcher - induced current in the ring such that its magnetic field opposes the magnetic field of the solenoid that created it. Its like two magnets repelling each other, and the ring flies up. Demo - several variations
Demo: run a DC generator backwards - its a DC motor!
Eddy currents are circular currents induced in the plane of a metal plate when passing through a changing magnetic field.
Video 23: "Eddy Currents: Force Acting on a Moving Conductor".
Current Balance Experiment - two horseshoe magnets - aluminum plate is a damper
|20.||Friday, Apr. 28|
Inductance of an inductor: L = NFB /
demo - digital inductance meter
Value of L depends on the geometry: L = m0N2 A / l
RL circuit, solve the differential equation for the circuit
Computer: Micasoft - M1 - inductors
Energy in a magnetic field, UB = 1/2 L i2, energy density in inductors and capacitors
Mutual inductance (when you have two coils)
|21.||Wednesday, May 3|
|22.||Friday, May 5|
Demo: R circuit -
function generator, R, speaker, DMM (on ac volts),
Capacitor circuits: capacitive reactance = XC = 1/wdC, VC = ICXC, vC lags iC by 90o
Inductor circuits: inductive reactance = XL = wdL, VL = ILXL, vL leads iL by 90o
RLC series circuit, i = Im sin wdt, phasor diagrams, impedance Z, V = IZ, Z = ..., tan f = (XL-XC) / R
Resonance in an RLC series circuit, f = 1 / 2p sqrt(LC), graph (p. 845), Demo: RLC circuit
Computer: Micasoft - M1 - resonance
Power in AC circuits
|23.||Monday, May 8|
Demo: show several examples
Video 24: "Voltage Transformer"
Chapter 32. Maxwell's Equations, Magnetism of Matter
|24.||Wednesday, May 10|
Curie's Law: M = C
(B / T), C = Curie constant, T =
absolute temperature, graph...
Properties of paramagnetic, ferromagnetic and diamagnetic materials
M = c H, c (chi) = magnetic suseptibility, p. 876: (paramagnetic) liquid oxygen suspended in a magnetic field Ferromagnetism, magnetic domains
Video 25: "Tesla - Master of Lightning" - We will watch the first 40 minutes. To be continued on Friday.
There will be one or two questions on Test 3 about what you learn from this video.
|25.||Friday, May 12|
1. AC Motor
|Last update: May 7, 2006|