Lots of Busy Brains

Honors Physics began their unit on magnetism with a discussion of magnetic fields and magnetic field lines. The directionality of magnetic fields was emphasized and standard permanent magnets and the Earth’s magnetic field was used as an example. Hard versus soft magnetic materials were introduced and students were given a look at hysteresis curves for a soft and hard magnetic substance. A lodestone was demonstrated to show that even the weak magnetic field of the Earth can magnetize an object, given enough time. Students were also introduced to the concept of electromagnetism and how the right-hand rule is used to predict the direction of the magnetic field in a current-carrying wire. Tomorrow’s lab will allow students to investigate permanent magnets. The nature of the magnetic dipole, field strength at distance and properties of different shapes of magnets will be explored.

Physical Science B and E worked on MCAS practice in preparation for tomorrow’s exam. Questions about waves were also tossed in, since students are still having some difficulty with wave concepts. After tomorrow’s exam, we will begin our unit on magnetism. Remember to have your circuits projects completed and turned in to me by Friday. Some folks in B-Block asked for Coulomb’s Law review problems, so I gave them this sheet and this sheet. The answers for these are below:
Coulomb’s Law Problems

1. 8.7 x 10⁶ N
2. 7.8 x 10^-14 m
3. 3.4 x 10^-7 C
4. 1.1 m
5. Charge must be negative, since the force with the other charge (which is negative) is a positive force
6. 1.2 x 10^-7 C

Unit 1 Worksheet 3: Coulomb’s Law

1. Electric force is directional proportional to the magnitude of the interacting charges and inversely proportional to the squared distance between them.
2. Force drops to 1/4 of the original value; force drops to 1/9 of the original value
3. F_g = 4.1 x 10^-47 N
4. F_e = 9.2 x 10^-8 N
5. The enormous discrepancy between the magnitude of the forces that the electric force has more impact on the behavior of the charges than does the gravitational attraction between them.
6. Both spheres should have force arrows for weight (down) and the normal force (up) that are equal in size. Much smaller arrows indicating electric forces repelling the spheres should be indicated as for a standard force diagrams.
7. Arrows should indicate equal forces acting on each particle indicating motion away from the neighboring particle. Magnitude of force = 1.3 N and the force is a repelling force.
8. 1.6 x 10⁴ N, repelling
9. -0.4 N, attracting
10. -40 N

Physics F and G slogged through their electricity exams. Tomorrow, we begin our discussion of magnetism by examining the basic nature of magnetic fields and magnetic field lines.

Homework

Honors Physics A: Read lab protocol sheet
Physical Science B: Complete electricity review worksheets and study for exam. Complete MCAS review packet by Thursday
Physical Science E: Study for exam. Complete all MCAS review packet questions by Thursday
Physics F and G: 20.1 Section Review and Chapter Review items #1-4