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Magnetic Fields, Magnetic Forces, and Electromagnetic Induction Sample Problems

  1. A wire 1 m long carries a current of 5 A. The wire is at right angles to a uniform magnetic field. The force on the wire is 0.2 N. What is the magnetic field strength?
  2. Now in number one, the wire is directed at an angle of 30°. What is the magnetic field strength?
  3. A 10 cm long wire is at right angles to a uniform magnetic field of 0.06 T. A 4 A current is in the wire. What magnetic force does it experience? What is the magnetic force if the wire was at an angle of 40° to the magnetic field?
  4. A beam of electrons travels at 3,000,000 m/s through a 0.04 T field. What force does the beam experience?
  5. A wire 2 m long moves perpendicularly through a 0.08 T field at a speed of 7 m/s. What emf is induced? Knowing Ohm’s law and that the wire has a resistance of 0.50 ohms, what current flows?
  6. The direction of a 0.045 T field is 60° above the horizontal. A wire 2.5 m long moves horizontally through this field at 2.4 m/s. What emf is induced in the wire?
  7. Calculate the strength of the magnetic field at a point 0.5 cm above a straight-wire conductor carrying 5 A, directed from left to right.
  8. Two parallel wires are separated by 5 cm .The wire on the left carries 8 A. The wire on the right carries 5 A. Calculate the magnitude and direction of the net magnetic field at a point 2 cm to the left of the 5 A wire. The currents flow up in both wires.
  9. Two parallel wires are separated by 5 cm .The wire on the left carries 8 A. The wire on the right carries 5 A. Calculate the magnitude and direction of the net magnetic field at a point 2 cm to the left of the 5 A wire. The current flows up in the wire on the left and down in the wire on the right. .
  10. An electron (mass = 9.11 x 10-31kg) travels at 2 x 107m/s in a circular path in a 0.010 T magnetic field. What is the radius of its path? What is its kinetic energy? Ans: 0.011 m; 1.82 x 10-16J
  11. What is the strength of the magnetic field necessary to balance a wire that has a mass of 5 g, is 3.5 m long, and carries 2 A?