PHYS 1112
Chapter 19 Problems

Chapter Objectives

  1. Calculate the force on a moving charge in a magnetic field and predict the motion of the charged particle.
  2. Calculate the force on a current in a magnetic field.
  3. Calculate the torque on a current loop in a magnetic field.
  4. Define Ampere's Law and calculate the magnetic field due to a current-carrying wire.
  5. Understand and use the relationship between the magnetic field, the current and the number of loops per unit length for a long solenoid.

Conceptual Questions

  1. The north-seeking pole of a magnet is attracted twoard the geographic north pole of the Earth; yet like poles repel. What is the way out of this dilemma?
  2. Can a magnetic field set a resting electron in motion? If so, how?
  3. Explain why two parallel wires carrying currents in opposite directions repel each other.

Problems

  1. A proton travels with a speed of 3.0 x 106 m/s at an angle of 37o with the direction of a magnetic field of 0.30 T in the +y direction. What are (a) the magnitude of the magnetic force on the proton and (b) the proton's acceleration?
  2. Imagine a very long, uniform wire with a linear mass density of 0.0010 kg/m that encircles the Earth at its magnetic equator. What are the magnitude and direction of the current in the wire that will keep it levitated above the ground?
  3. A wire with a mass of 1.00 g/cm is placed on a horizontal surface with a coefficient of friction of 0.200. The wire carries a current of 1.50 A eastward and moves horizontally to the north. What are the magnitude and direction of the smallest magnetic field that enables the wire to move in this fashion?
  4. A proton moves in a circular orbit perpendicularly to a uniform magnetic field of 0.758 T. Find the time it takes the proton to make one pass around the orbit.
  5. Figure 20-29 is a cross-sectional view of a coaxial cable (such as a VCR cable). The center conductor is surrounded by a rubber layer, which is surrounded by an outer conductor, which is surrounded by another rubber layer. Suppose that the current in the inner conductor is 1.00 A out of the page, and the current in the outer conductor is 3.00 A into the page. Using Ampere's law, determine the magnitude and direction of the magnetic field at a point between the conductors and outside of the cable.

Solutions

If you find an error in these, or just have a comment, send an e-mail message to jpratte@kennesaw.edu