|1.||Monday, Mar. 8 - 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. 10|
Series - shows how strongly various materials hang on to their
electrons when you rub them together.
List of 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. 12|
Computer - EM Field program - 3D
sources (Start, Physics, EM Fields) - also
available on the computers in 204 and 121
|4.||Monday, Mar. 15|
Motion of a charged particle in a uniform electric field
Applications: oscilloscope, shadow of an electron beam, TV, computer monitor, ink jet printing (p. 592, Fig. 22-15)
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 Fig. 22-19
Chapter 23. Gauss' Law --
electric flux, Φ
= E A cos θ
= ... (integral of E dot dA)
|5.||Wednesday, Mar. 17|
Gauss' law: For any closed surface, electric flux
qin / ε0 where
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 λ. E = 2k λ / r. Fig. 23-12
Computer - EM Field - Options, Display Gauss' Law.
4. Nonconducting, infinite plane sheet with surface charge density σ. E = σ/2ε0 (indep. of r) Fig. 23-15
5. Conducting surface with surface charge density σ. E = σ/ε0 (indep. of r) Fig. 23-10
|6.||Friday, Mar. 19|
Chapter 24. Electric Potential.
Analogy: gravitational field --- electric field
Definition of potential difference, ΔV = ΔU / 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".
|7.||Monday, Mar. 22|
Applications of Electrostatics
Xerography - invented by Chester F. Carlson in 1937. How Photocopiers Work - How Laser Printers Work
Lightning - one minute exposure at Kitt Peak National Observatory in Arizona
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, schematic drawing - Demo: stack of aluminum plates, blue-gold wig, spinner
|8.||Wednesday, Mar. 24|
Computer - EM Field - equipotential lines
Recall: ΔU = q ΔV
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 Fig. 22-16
Demo - induction coil
Capacitor - any two conductors separated from one another by an insulator
Definition: C = Q/V, capacitance is measured in farads (F), 1 F = 1 C/V
Parallel plate capacitor drawing...
Demo - Pasco aluminum plates - one fixed, the other moveable on a track
E = V/d, symbols for a capacitor..., C = εoA/d
Isolated spherical conductor of radius R: C = R/k
Derivation for a cylindrical capacitor
Derivation for a spherical capacitor
|9.||Monday, Mar. 29|
Capacitors with dielectrics, C =
κ εo A/d
= κ Co,
κ = 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 11. "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.
Energy stored in capacitors = U = ½ CV2
|10.||Wednesday, Mar. 31|
Add a dielectric to a capacitor: U = U0/κ
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 12: "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 13: "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 = σE, V = i R
Resistivity ρ of a wire of length L, cross-sectional area A and resistance R, R = ρ L / A. Table 26-1 Table for α
Variation or resistivity with temperature, demo: heat a resistor, meas. R with the 4-digit DMM, it decreases slightly
|11.||Wednesday, Apr. 7|
14: "Temperature and Resistance"
Color codes for resistors:
Joule's Law for resistors: P
= i2R =
Vi = V2/R
|12.||Friday, Apr. 9|
1. At Fermilab magnetic windings (wires) are cooled with liquid helium (4.2 K) so the wires are below Tc resulting in
a tremendous savings in electricity (practically no "Joule heating"). The magnetic field of each 7-meter tubular
magnet is 4.5 tesla.
2. "maglev" (magnetic levitation) trains in Japan, Germany and China (Shanghai).
3. Superconducting magnet in Science 114 - part of the 400-MHz NMR (nuclear magnetic resonance) equipment. The
outer part is cooled by liquid nitrogen (77 K). The inner part is cooled by liquid helium (4.2 K). The magnetic field is
very strong (9.7 tesla) and is well regulated. This field is created by means of a solenoid (coil of wire). The wire
consists of very fine strands of superconducting niobium-titanium clad in copper. This is a Type II superconductor
with a critical temperature Tc = 10 K. NMR slides taken Jan. 20, 2004. NMR cutaways - JEOL
Chapter 27. Circuits
|13.||Monday, Apr. 12 - went over Test 1|
Example of using Kirchhoff's rules - two batteries, 7
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
Video 16: "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.
|Discussion, Tuesday, Apr. 13|
Example of using Kirchhoff's rules - 3 equations in 3 unknowns
|14.||Wednesday, Apr. 14|
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).
RC circuit, charging C, time constant = τ = RC, discharging C.
Demo on the computer: Micasoft - M1 - capacitors
Chapter 28 - Magnetic Fields
|15.||Friday, Apr. 16|
Explore with the
Earth's magnetic field,
Demo - ball (Earth) containing a magnet
Video 17: "Mapping Magnetic Field Lines"
(magnetic declination) = (direction of true north) - (direction of magnetic north) = 2o east of north at Augustana 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 θ, direction of Fm is perpendicular to the plane containing v and B.
Memory devices: 1. three-finger rule. 2. alternate right-hand rule.
Video 18: "Forces on an Electron Beam"
Demo: show the corresponding apparatus
Two special cases: 1. v parallel to B, 2. v perpendicular to B. Uniform circular motion, r = mv / qB
Examples: the Tevatron at Fermilab and the Large Hadron Collider at CERN
If v is not parallel to B: spiral path. Occurs in nature around BEarth - produces the aurora borealis Fig. 28-12
photos of Nov. 5, 2001 | SpaceWeather.com | Aurorawebcam.com
|16.||Monday, Apr. 19|
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)
Fig. 28-20 (electric motor). Torque on a current loop in a magnetic field. torque = τ = N i A B sin θ. DC electric motor
General form for a current loop: torque vector = τ = i A x B = μ x B, μ = i A = magnetic moment
Another torque application: Galvanometer - add a coil spring. Fig. 28-22.
Chapter 29. Magnetic Fields Due to Currents
|17.||Wednesday, Apr. 21|
Two parallel current carrying wires
Video 19: "Forces on a Current Carrying Wire"
Demo: Current balance apparatus that will be used in lab
Magnetic field around a single current loop
Computer: EMfield - magnetic field around a single current loop Fig. 29-23
Current loop as a magnetic dipole, μ = i A. Compare to the magnetic field around a bar magnet: Fig. 29-22
Ampere's Law - For any closed path around a one or more wires carrying a current,
line integral ( B . ds ) = μ0 ienc. The integration loop is called an Amperian loop.
Computer: EMField - explain Ampere's Law, file: isheets.emf
Magnetic field inside a long solenoid: B = μ0 n i n = no. of turns per meter
Demo: Fig. 29-19 Short solenoid, measure B with the digital Tesla meter B = (0.5) μo n i (sin φ2 - sin φ1)
|18.||Friday, Apr. 23|
Computer: EMfield - file: coaxmag.emf
Chapter 30. Induction and Inductance
|19.||Wednesday, Apr. 28|
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, ξ = 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) Drawing and schematic - alternating current generator
ξ = N B A ω sin (ωt), ω = the angular frequency (in rad/s), ω = 2πf, f = freq. in Hz
Demo: generator #1 - incandescent bulb, flicker bulb
|20.||Friday, Apr. 30|
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
|21.||Monday, May 3|
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 21: "Eddy Currents: Force Acting on a Moving Conductor".
Current Balance Experiment - two horseshoe magnets - aluminum plate is a damper
Inductance of an inductor: L = NΦB / i demo - digital inductance meter
Value of L depends on the geometry: L = μ0N2 A / l
RL circuit. Fig. 30-18 Differential equation for the circuit, solution for the current,
graph, inductive time constant = τL = L / R
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) Fig. 30-23
|22.||Wednesday, May 5|
|23.||Friday, May 7|
Demo: R circuit -
function generator, R, speaker, DMM (on ac volts),
Fig. 31-8 - R circut
|24.||Monday, May 10|
Demo: show several examples
Video 22: "Voltage Transformer" Fig. 31-15
Power transmission from the power plant to the home - Transformer sequence
Chapter 32. Maxwell's Equations, Magnetism of Matter
|25.||Wednesday, May 12|
Curie's Law: M = C
(Bo / T), C = Curie constant, Bo
= external magnetic field,T = absolute temperature
Properties of paramagnetic, ferromagnetic and diamagnetic materials
M = χ H, χ (chi) = magnetic suseptibility, p. 876: (paramagnetic) liquid oxygen suspended in a magnetic field Ferromagnetism, magnetic domains Fig. 32-17 (domains in nickel)
Video 23: "Tesla - Master of
Lightning" - We will watch the first part. To be continued on
|26.||Friday, May 14|
Video 23: "Tesla - Master of
Lightning" - We will watch the remaining 40 minutes.
Go to the Web page Tesla - Inside the Lab to obtain a description of Tesla's most important inventions:
1. AC Motor
|Last update: May 13, 2010|