Download Pre-class test FISI-3171

Exam 3
FISI-3172
Oct. 27, 2009
Dr. LU
(Write your answers on the answer sheets.)
1. When two parallel wires have current flowing in the same direction, the mutual force
they experience will be? (5 points)
a) attractive.
b) repulsive.
c) zero.
2. A static electric field is conservative, but an electric field produced by a changing
magnetic field is nonconservative. (5 points)
a) True.
b) False.
3. A time constant of an LR circuit is equal to: (5 points)
b) L/R.
c) R/L.
d) 1/(LR).
a) LR.
4. The SI unit for inductance is the. (5 points)
a) Newton.
b) Faraday.
c) Henry.
d) Coulomb.
5. A rectangular loop of wire is placed next to a straight
wire, as shown in the right Figure. There is a current of
3.5 A in both wires. Determine the magnitude and
direction of the net force on the loop. (20 points)
6. A 40.0-cm-long solenoid 1.35 cm in diameter is to
produce a field of 0.385 mT at its center. How much
current should the solenoid carry if it has 765 turns of
wire? (20 points)
7. To make the rod move to the right at speed v, you
need to apply an external force on the rod to the right.
(a) Determine the magnitude of the required force. (b)
What external power is needed to move the rod? (20
points)
8. A 1200-pF capacitor is fully charged by a 500-V dc power supply. It is disconnected from
the power supply and is connected, at t = 0, to a 75-mH inductor. Determine: (a) the
initial charge on the capacitor; (b) the maximum current; (c) the frequency f and period T
of oscillation; and (d) the total energy oscillating in the system. (20 points)
Bonus problem (20 points) Determine the direction of the induced current in each loop.
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FISI-3172
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