Week 23 (Jan. 29 - Feb. 2)

Reading: Magnetic fields (Chap. 29)

Key Topics:
magnetic poles, earth's magnetic field, magnetic materials, ferromagnetism, paramagnetism, curie temperature,
Lab: Magnetism laboratory

Homework Problems: Due Tuesday, Feb. 7
  1. Magnetized compass needle: Carefully sketch the orientation of a magnetized compass needle when placed at several locations in the vicinity of a spherical ``terrella" (a) which is unbroken, (b) which has been split in half along the equator and the two halves slightly separated, (c) which has been split in half along a line joining the poles. Be sure to label the magnetic north ends of the terrella and the compass needle so things are oriented correctly.
  2. Magnetic field lines: Sketch the magnetic field lines in the vicinity of (a) a bar magnet, (b) two bar magnets placed end-to-end, slightly separated, with the north of one facing the south of the other, (c) same as previous but with the north poles facing one another, (d) a circular loop of wire carrying an electrical current, (e) a long helical coil of wire carrying an electrical current.
  3. Electron near earth's equator: Consider an electron near earth's equator. In which direction will it be deflected if its velocity is directed (a) downward, (b) northward, (c) westward, (d) southeastward?
  4. Suspending a wire magnetically: A wire having a mass per unit length of 0.5 grams/cm carries a 2.0 ampere current horizontally to the south. What are the magnitude and direction of the minimum magnetic field needed to lift this wire vertically?
  5. Proton in a magnetic field: A proton is moving at 4000 km/sec through a magnetic field of 1.7 tesla. It experiences a force of 8.2e-13 Newtons. (a) What is the angle between the proton's velocity and the field? (b) Is it possible for the field to exert zero force on the moving proton? If so, how?
General College Physics