Discussion Notes for Monday, June 30, 2008Prepared by: Aaron WessellConceptual Problems(Kim Rosenthal borrowed it from pg. 495 in Essentials of College Physics)1) A charged particle moves in a straight line through a region of space. Which of the following answers must be true? (assume any other fields are negligible). The magnetic field(a) has a magnitude of zero(b) has a zero component perpendicular to the particle's velocity(c) has a zero component parallel to the particle's velocity in that region.-C can be either True or False, it does not necessarily have to be true.* A magnetic field parallel to the direction of the charge’s velocity would not affect the motion of the charge.(Kim Rosenthal borrowed it from pg. 515 # 10 in Essentials of College Physics)2) Will a nail be attracted to either pole of a magnet? Explain what is happening inside the nail when it is placed near the magnet.-Atoms can possess dipole moments. When brought close to the magnet, the dipole moment aligns with the magnetic field and the atom becomes a magnet of its own. Therefore, the nail can be attracted to either pole of the magnet. (Monique Pogreba borrowed it from pg. 514, #6 in Essentials of College Physics)3) Which way would a compass point if you were at the earth's North magnetic pole? Why?-The needles of a compass align with, and point in the direction of, the magnetic field. In order to know what direction the needle will point, one must know what the magnetic field of Earth looks like. The Earth’s geographic North pole is actually a magnetic South pole.-If a vertical compass is placed at the North pole it will point directly down towards the North pole.(Monique Pogreba borrowed it from pg. 514 #2 in Essentials of College Physics)4) Can a constant magnetic field set a proton at rest into motion? Explain your answer.-According to the following equation: FB=qvBsinθ, a constant magnetic field cannot set a proton at rest into motion. If the charge is not moving, its velocity is zero, and if the velocity of zero, the force applied by the magnetic field is zero.-Shushaku also reminded us that in dealing with electrostatics, the force on a charge in an electric field is in the direction of the electric field. However, with magnetism, the force applied by the magnetic field is in a direction perpendicular to the magnetic field.Quantitative Problems(Tim Ford borrowed it from Essentials of College Physics, pg. 516 - # 8)1) An electron is accelerated through 2,400 V from rest and then enters a region where there is a uniform 1.70-T magnetic field. What are (a) the maximum and (b) the minimum magnitudes of the magnetic force acting on this electron.-As the electron is accelerated through 2,400 V from rest its potential energy will be converted into kinetic energy, which allows for one to solve for the velocity: PE = Vq PE = (2400 V)(-1.6e-19C) PE = 3.84e-16J= (1/2)mv2 v = 2.903e7 m/sFmax = qvB (no need for sinθ when dealing with the max) = (-1.6e-19C)(2.903e7 m/s)(1.7) = 7.88e-12 NFmin = 0, if the magnetic field is parallel to the motion of the electron. If sinθ = 90 or 180 degrees, then F is max = 0 or 360 degrees, then F is min(Katie Daniel borrowed it from Essentials of College Physics, pg. 516 # 14)2) A wire having a mass per unit length of 0.500 g/cm carries a 2.00-A current horizontally to the south. What are the direction and magnitude of the minimum magnetic field needed to lift this wire vertically upward?-We will focus on this problem later on because it is more involved.CLOSING REMARKS:-Tomorrow will be used as a Q + A session in preparation for Wednesday’s exam.-Shushaku would like for questions to be sent to him via email, along with a sentence or two describing what you are having trouble with. He will try to address common questions in discussion.-Tomorrow’s discussion attendance is optional. Those who wish to use the 50 min for independent study time may do so.-Shushaku has to leave discussion 10 min early but may be seen during his office hours before lecture in Room 4257, Chamberlin.-Reminder: Lab has been changed to 12:45 pm on Tuesday, except for those attending the lab session on