Unformatted text preview: Physics 171.102 Exam 2 October 31, 2002
Prof. Barnett Write your TA’s name, conference time and your name on each blue book. Write everything in ink.
You may utilize material written on both sides of ONE 3”x5” index card. 1. The adjacent circuit includes a switch, a 3 volt battery,
three resistors (R1 = 19, R2 = 252, R3 : 2(2) and one
capacitor (C : 10pF). The switch is initially open so there R = 29
is no charge on the capacitor and no current in any resistor. 2
At t = 0 the switch is closed and remains closed. 3W;olt A) (10 pts) What is the maximum instantaneous
current that ever ﬂows through resistor R1? B) (10 pts) What is the maximum potential
difference that is ever across the capacitor? B) (10 pts) What is the maximum instantaneous
power ever dissipated in resistor R3? 2. The adjacent ﬁgure shows a square wire with sides
of length 10 cm It carries a current of 0 1 amperes.
It is mounted in the x— y plane. There 13 a uniform
magnetic ﬁeld B— — 4.0 i —\5. 0 k Tesla 1n the region. K J A) (10 pts) What is the magnetic moment vector of the loop???
B) (10 pts) What is the torque, ?, on the wire loop about an axis through it center of mass? C) (10 pts) What is the total magnetic ﬂux through the loop due to the external uniform B
ﬁeld in the initial conﬁguration? 3. An airplane is ﬂying horizontally over the South Pole, i.e. over Antarctica, at a speed of
360 km/hr. The magnitude of the vertical component of the earth’s magnetic ﬁeld is 5 x10‘5 T
at the location of the plane. The plane has a wingspan of 20 meters and a length of 15 meters. A) (10 pts) What is the induced emf between the wing tips?
B) (10 pts) What is the induced emf between the plane’s nose and tail?
C) (5 pts) Will the wing to the pilot’s left or to the pilot’s right be at the higher potential? 4. (15 pts) A 100 ohm resistor is in series with a 5 HF
capacitor and a 0.2 -H inductor. The circuit is
driven by a sinusoidal power source. What is the
angularpfrequency (radians per second) of the power ,
source if the total impedance of the circuit is 100 ohms? Vo cos(rot) 100 ohms ...
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