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Physics 232
Exam 3
Name ______________
1. A horizontal metal rod (oriented in the east-west direction) is moved northward at
constant velocity through a magnetic field that points straight down. Which statement is
true?
a) The west end of the rod is at higher potential than the east end.
b) The east end of the rod is at higher potential than the west end.
c) The top surface of the rod is at higher potential than the bottom surface.
d) The bottom surface if the rod is at higher potential than the top surface.
2.
a)
b)
c)
Consider an LRC circuit. The impedance of the circuit increases if XL increases.
Always true
True only if XL is less than or equal to XC
True only if XL is greater than or equal to XC
3. When an emf is induced in coil 2 of a mutually inductive pair of coils, the emf can be
related through mutual induction to
a) the current in coil 1
b) the change in current in coil 1
c) the rate of change of current in coil 1
d) none of the above
4. An EM wave is traveling to the East. At a given point in time the magnetic field is
upward. What is the direction of the electric field for the wave?
a) north
b) south
c) east
d) west
e) down
f) up
5. What is the direction of the induced current in the circular loop due to the current
shown in each part. (8 pts)
6. A single rectangular loop of wire with the dimensions shown is situated so that part is
inside a region of uniform magnetic field of 0.450 T and part is outside the field. The
total resistance of the loop is 0.230 Ω.
a) If the loop moves at a constant velocity of 3.40 m/s, how much does the flux change
in 0.1 second? (5 pts)
b) Calculate the force required to pull the loop at a constant velocity of 3.40 m/s.
Neglect gravity. (10 pts)
7. It takes 4.53 ms for the current in an LR circuit to increase from zero to three-fourths
of its maximum value. Determine the resistance of the circuit if L = 310 H. (12 pts)
8. What is the frequency of a microwave whose wavelength is 1.80 cm? (5 pts)
9. A capacitor is placed in parallel with some device, B, as shown to filter out stray high
frequency signals but to allow ordinary 60 Hz AC to pass through with little loss.
Suppose the circuit B in the figure has a resistance R = 400 Ω connected to ground and
that C = 0.35 µF. What percent of the incoming signal will pass through C rather than R
if (a) it is 60 Hz; (b) 60,000 Hz? (10 pts)
10. WEAU TV Channel 13 in Eau Claire has a tower that transmits with a power of 316
kW. In Fall Creek, 16.1 km away,
a) What is the energy per unit time per unit area for the wave? (5 pts)
b) What is the rms value of the electric field? (5 pts)