1. Monday(02/22): Intro. to Ch.21 - Magnetism and Magnetic Fields.

Forces on Current-carrying Wires, Forces on Charged Particles, and the

Right-Hand Rules. HW: Read and Study pages 621-29, then solve

problems 1, 5, 9, 10, and 15 on pages 653-54.

2. Tuesday(02/23): The Mass Spectrometer, Force on a Current,

and Magnetic Field of a Current. HW: Read and Study pages 630-38,

and pages 644-51, then you should solve problems 23, 27, 46, and 47

on pages 654-56.

3. Wednesday(02/24): LAB on Magnetic Fields of Magnets and Coils.

HW: Process lab data. Lab Report due Monday.

4. Thursday(02/25): Intro. to Ch.22 - Electromagnetic Induction,

Induced and Motional Emf, and Magnetic Flux. HW: Read and Study

pages 660-67, then solve problems 1, 5, 12, and 13 on pages 689-90.

5. Friday(02/26): No School due to Teacher Meeting Day. HW: Finish

all assigned work.

6. Monday(03/01):Faraday's Law, Lenz's Law, and Transformers. 

HW: Read and Study pages 667-72, and pages 681-88 then solve

problems 17, 25, 28, 54, and 58 on pages 690-93.

7. Tuesday(03/02): Class does not meet due to FCAT Practice from

8:40 to 12:30. Then Lunch and Periods 5, 6, 7. HW: Finish all assigned

work.

8. Wednesday(03/03): Review for Ch.21 and 22. HW: Complete Review

Handout.

9. Thursday(03/04): TEST on Ch.21 & 22. HW: Go to website and

study notes for Ch.23 - Electromagnetic Waves.

Best to send an email to rpersin@fau.edu.

1. The force F produced by a magnetic field on a single charge depends upon

the speed v of the charge, the strength B of the field in N/Am or Tesla, T,

and the magnitude of the charge q, with F = qvBsinθ. θ is the smaller angle

between v and B. 

2. To find the direction of the force, use the First Right-Hand Rule with your

fingers in the direction of B, and your thumb in the direction of v. The force

will come out of the palm of your hand.

3. If the charged particle moves parallel to the field lines (θ = 0), then the

magnetic force on the particle is zero. If a charged particle is moving

perpendicular to a uniform magnetic field, the path of the charged particle

is an arc (or circle).

4. The strength of the magnetic field depends on the current I in the wire

and r, the distance from the wire. The equation is B=μ_oI∕(2πr) , with the

constant μ_o, "mu naught", given as μ_o = 4π x 10^-7 Tm/A .

5. The constant is the permeability of free space. The reason it does not

appear as an arbitrary number is that the units of charge and current

(coulombs and amps) were chosen to give a simple form for this constant.

6. The magnetic force is the source of the centripetal force on the charged

particle. This relationship can be used to find the radius of the arc when we

set the equations equal to one another,  mv²/r = qvB , and solve for r.

7. Since the magnetic force is perpendicular to the velocity of the charged

particle, the force does not cause the speed of the particle to change, only

its direction. Thus, no work is done by the magnetic force on the charged

particle.

8. In regards to forces due to magnetic fields, Ampere found that a force is

exerted on a current-carrying wire in a magnetic field, F = BILsin θ, where

B is the magnetic field in N/Am, I is the current, L is the length of wire

in meters, and θ is the angle between B and L.

9. If the direction of the current is perpendicular to the field (θ = 90), then

the force is given by F = BIL.

10. If there is also a magnetic field between two charged plates in

addition to the electric field, and the fields are crisscrossed, that allows the

charge to pass through undeflected, qE=F, and F=qvB , yields v = E/B.

11. Again, for regions where both electric and magnetic fields exist:

V=Ed, qE=F, and F=qvB. Manipulating these formulas allows you to write an

expression for the accelerating voltage in terms of v, B, and d.

12. When a conductor of length, L, and velocity, v, moves across a magnetic

field, B,  an Electromotive Force (Emf), ε, is induced in the conductor. This is

given by ε = BLv.

13. The current in the conductor is now given by I = ε / R, which is now

Ohm's Law for current from induced Emf.

14. The total magnetic flux through a plane area, A, placed in a uniform

magnetic field depends on the angle between the direction of the magnetic

field and the direction perpendicular to the surface area. The equation is

Φ = BAcos(θ) .

15. Faraday discovered that when the magnetic flux, given by the Greek

letter Phi, Φ, changes with time, an electromotive force, or Emf, is produced.

Or we can say, ε = -N∙ΔΦ/Δt , with N as the number of turns in the coil.

16. Since the magnetic flux is the product of the magnetic field, B, the area,

A, and the cos of the angle between the magnetic field and the normal to

the surface, there are three possible ways the flux can change with time;

the field, B, or the area, A, or the angle theta.

17. Lenz's Law: The polarity of the induced Emf is such that it tends to

produce a current that will create a magnetic flux to oppose the change in

flux through the circuit, ε = -ΔΦ/Δt .

18. Remember that a generator changes mechanical energy to electrical

energy. But a motor does the opposite. It changes electrical energy to

mechanical.

19. In many cases voltage must either be "stepped-up" or "stepped-down"

depending on the application. These processes rely on transformer equations,

which are P_P = P_S , which means that the power of the primary circuit equals

the power generated in the secondary, if ideal.

20. Therefore, since P = VI , we have V_P∙I_P= V_S∙I_S . Physically this is

accomplished by the number of turns, N, in each coil. Now we have the

equation, V_P/V_S= N_P/N_S .

21. And still, we need these steps to solve any problem in Physics:

(i) read the problem and identify the given variables

(ii) determine what you are asked to solve for

(iii) find the correct equation to use

(iv) use Algebra, Trigonometry, and/or Calculus to isolate the unknown

(v) substitute-in the given information and simplify.

THE AP PHYSICS B ARCHIVES Ch.1: Physics Intro. Ch.2: Linear Motion. Ch.3: 2-Dim Motion. Ch.4&5: Newton's Laws. Ch.6: Work/Energy. Ch.7: Momentum. Ch.8&9: Rotary Motion. Ch.10: SHM. Ch.11: Fluids. Ch.12&13: Temp.&Heat. Ch.14&15: Thermodynamics. Semester Review. Ch.16: Waves & Sound. Ch.17: Wave Interference. Ch.18: Electric Fields. Ch.19: Electric Potential. Ch.20: DC Circuits.