Magnetic Fields and Electromagnetic Induction --- Quiz

Name: ______

Date: ______

  1. Give two reasons that electromagnets are more widely used than natural magnets.
  1. What is the nature of magnetic force?
  1. Usually an electromagnet is composed of a solenoid and an iron core. What’s the role of the iron core?
  1. In what way(s) can the strength of an electromagnet be increased?
  1. How is it that one magnet can repel or attract another magnet even when they are not in direct contact?
  1. What properties a magnetic field has?
  1. Where is the magnetic north pole of the Earth located?
  1. Draw a graph to show the direction and strength of the magnetic field around a permanent bar magnet.
  1. A straight wire 0.20 m moves perpendicularly through a magnetic field of magnetic induction 0.008 T at a speed of 7.0 m/s. What electromotive force (EMF) is induced in the wire?
  1. If you broke a magnet in two, would you have isolated north and south poles? Explain.
  1. When a wire is moved through a magnetic field, will resistance of the closed circuit affect the current, or EMF, or both?
  1. Indicate the two poles of the electromagnet shown.
  1. Some materials show polarity. What is it about those materials that allows them to exhibit such a property?
  1. Derive the relationship of effective current strength Ieff and maximum current strength Imax.
  1. Please explain the principle of operation of an electric motor.
  1. Please explain the principle of operation of an electric generator.
  1. Please tell me everything you know about alternating current (AC).
  1. What is the difference between a generator and a motor in view of energy utilization and conversion? Can these devices create energy?
  1. If a current-carrying wire is bent into a square loop, why is the magnetic field inside the loop stronger than the magnetic field outside?

(Tip: consider the direction of B generated by each side of the loop.)

  1. Indicate graphically the direction of B generated by the two currents, respectively, and the direction of the magnetic forces exerted on the currents.