Unit 10 AP Review Problems---Electromagnetism

In order to do well on this test you need to truly understand every single thing that was taught in this and the previous two units (circuits and magnetism). Please don’t let the fact that there are only five review problems lull you into a false sense of security. My advice to you is to go back and re-do every single practice problem in this unit before you do the review problems just to make sure that these five problems are actually a “review” for you.

  1. The area of a 333-turn conducting coil is 7.85  103 m2. The resistance of the coil is 10.4 . If the coil is oriented as shown in a magnetic field B, at what rate in T/s should the magnitude of B change to induce a current of 2.50  103 A in the coil? (1.55 E-2 T/s)
  1. A long, straight wire is in the same plane as a rectangular, conducting loop. The wire carries a constant conventional current I as shown in the figure.
  2. What will be the direction of the induced magnetic field inside the loop? (out of the page)
  1. What will be the direction of the induced current in the loop? (counter-clockwise)
  1. A sheet of copper is pulled at constant velocity v from a region that contains a uniform magnetic field of unknown direction. At the instant shown in the figure, the sheet is partially in and partially out of the field. The induced emf in the sheet leads to the eddy current inside the sheet as shown.
  2. Is the flux increasing or decreasing inside the sheet? How do you know? (decreasing)
  1. What is the direction of the induced magnetic field inside the loop of the eddy current in the sheet? (out of the page)
  1. What is the direction of the original magnetic field? How do you know?(out of the page)
  1. A circuit is pulled with a 16-N force toward the right to maintain a constant speed v. At the instant shown, the loop is partially in and partially out of a uniform magnetic field that is directed into the paper. As the circuit moves, a 6.0-A current flows through a 4.0- resistor.
  1. Is the flux increasing or decreasing inside the loop? How do you know?(decreasing; the loop is moving OUT of the field)
  1. What is the direction of the induced magnetic field inside the loop? (into the page)
  1. What is the direction of the induced current? (clockwise)
  1. What is the power dissipated by the resistor? (144 W)
  1. A loop with a resistance of 2.0  is pushed to the left at a constant speed of 4.0 m/s by a 32 N force. At the instant shown in the figure, the loop is partially in and partially out of a uniform 0.7 T magnetic field of unknown directionthat is perpendicular to the surface of the loop. An induced current flows from left to right through the resistor. The length and width of the loop are 2.0 m and 1.0 m, respectively.
  1. What is the direction of the induced magnetic field inside the loop? (out of the page)
  1. Is the flux increasing or decreasing? (increasing)
  1. What is the direction of the existing magnetic field? (into the page)
  1. What is the magnitude of the induced emf? (2.8 v)
  1. What is the magnitude of the induced current? (1.4 A)
  1. What is the total energy dissipated as the loop is pushed through the field? (1.96 J)
  1. A 2.0-kg rod has a length of 1.0 m and a resistance of 4.0 . It slides with constant speed down a pair of frictionless vertical conducting rails that are joined at the bottom. Other than the rod, the rest of the circuit is resistance-less. A uniform magnetic field of magnitude 3.0 T is perpendicular to the plane formed by the rod and the rails as shown. Determine the speed of the rod. (8.71 m/s)
  1. A conducting loop has an area of 0.065 m2 and is positioned such that a uniform magnetic field is perpendicular to the plane of the loop. When the magnitude of the magnetic field decreases to 0.30 T in 0.087s, the average induced emf in the loop is 1.2 V. What is the initial value of the magnetic field? HUGE note: The negative sign in Faraday’s Law must be used in this problem or you will get a completely wrong answer. (1.91 T)
  1. A circular loop of copper wire with an area of 2.0 m2 lies in a plane perpendicular to a time-dependent magnetic field directed out of the page as shown. The time-dependence of the field is shown in the graph.

What are the induced emf and the direction of the induced current during each of the following times?

  1. 1 s ( there is no change in flux so there is no induced emf)
  2. 4 s (+2.5 v, counterclockwise)
  3. 5 s (+2.5 v, counterclockwise)
  4. 7 s (-10 v, clockwise)
  5. 10 s ( there is no change in flux so there is no induced emf)

1

Unit 10 AP Review Problems EMag