Figure 1
Np = 1000
Ns = 100


Figure 2


Figure 2a


Figure 3


Figure 4


Figure 5  The induced emf causes an
induced current I to appear in the circuit.


Figure 6

PHYS 212 College Physics II
Final Practice Problems

  1. Consider the transformer shown in Figure 1. 120 Volts AC is applied to the primary winding. The primary coil has 1000 turns and the secondary has 100 turns. What is the magnitude of the current I, in the 200 Ohm resistor?

  2. What is the equivalent resistance between the points A and B in Figure 2?

  3. What is the voltage at node A in Figure 3? The Voltage at node B is zero.

  4. Consider the circuit shown in Figure 2a.

    • Vb = 12 Volts
    • R1 = 1000 Ohms
    • R2 = 1500 Ohms
    What is the voltage across R2, Vo?

  5. Obtain an expression for the force on the loop carrying the current I2 shown in Figure 4.

  6. The electric field in a 12.5 MHz electromagnetic wave propagating in the x direction is described by,
    1. What is the value of w ?

    2. What is the value of b ?

    3. What is the intensity of the wave?

  7. At one time television sets used "rabbit-ears", antennas. Such an antenna consists of a pair of metal rods. The length of each rod can be adjusted to be one-quarter of a wavelength of an electromagnetic wave whose frequency is 60 MHz.
    How long is each rod?

  8. The distance between earth and the moon can be determined from the time it takes for a laser beam to travel from the earth to a reflector on the moon and back. If the round trip time can be measured to an accuracy of one-tenth of a nanosecond (1ns = 10-9 s), what is the corresponding earth-moon distance?

  9. Suppose the light in Figure 5 has a resistance of 0.6 Ohms and consumes 15 W of power. The conducting bar moves to the right at a constant speed, the field strength is 2.4 T, and the length of the bar between the rails is 1.2 m.

    1. How fast is the bar moving?
    2. What force must be applied to the bar to keep it moving to the right at the constant speed found in part (a)?

  10. A long, straight wire lies on a table and carries a current I. As shown in Figure 6, a small circular loop of wire is pushed across the top of the table from position 1 to position 2.
    Determine the direction of the induced current, clockwise or counterclockwise, as the loop moves past
    1. position 1 and
    2. position 2.
    Justify your answers.

  11. In the polarizer/analyzer combination in Figure 7, 90.0% of the light intensity falling on the analyzer is absorbed.
    Determine the angle between the transmission axis of the polarizer and the analyzer.

    Figure 7