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Unformatted text preview: Physics 171.102 Exam 1 March 13, 2001
Prof. Barnett Write your TA’s name 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. 6,, = 8.85 x 101202/(Nm2) 1. Consider the adjacent circuit made of a 3.0 volt battery, two capacitors with Cl 2 1 0f and C2 = 2 ,uf, three resistors
with R1 2 59, R2 = 10 Q, and R3 = 30 Q,
and a switch. Initially, the switch is open so the battery is disconnected from
the rest of the circuit. At t=0 the switch is
closed connecting the battery to the circuit. A) (5 pts) Immediately after the switch is closed, ife. at t=0, what is the total energy stored
on each of the two capacitors?. B) (5 pts) Immediately after the switch is closed, i.e. at t=0, what is the current ﬂowing
through resistor R2? C) (5 pts) Immediately after the switch is closed, i.e. at t=0, what is the total power being
dissipated in resistor R2? D) (5 pts) A long time after the switch is closed, i.e. at t=oo, what is the total energy stored
on each of the two capacitors? E) (5 pts) A long time after the switch is closed, i.e. at t=oo, what is the current ﬂowing
through resistor R2? G) (5 pts) A long time after the switch is closed, i.e. at t=oo, what is the total power being
dissipated in resistor R2? 2. A graph of the electric potential as
a function of x is given in the adjacent
plot. The potential does not depend upon
y or z. A) (10 pts) Find the electric ﬁeld, E($, y, Z),
everywhere in this domain of X. B) (5 pts) Make an accurate plot of the
electric field for this domain of x. :‘140 0'30 02  , ., __+
. — . — . — . 0 o.1o 0.10 0.20 0.30 0.40
C) (20 pts) Describe in words what charge 5 —50 W“)
distribution could create this electric E [
ﬁeld and evaluate quantitatively the l ~100_ appropriate charge densities. 3. Particles with charge ( = 40—17 coulombs ), mass ( m = 10.27 kg) and velocity ( r7 = 2 X 106 m/sec 2' ) enter a region with a is uniform electric ﬁeld of E = 2 x 1025' N/C. E 2 2 x 1025 we
____________ l A) (10 pts) Draw a sketch of the particle’s 27 = 2 X 106 m/sec i hyperbola, ellipse, circle, parabola, etc.) and ﬁnd
the functional form of y and z for the trajectory trajectory, name the trajectory (e.g. straight line, 1
versus x (e.g. 2(22) : ”13123: + 3). B) (10 pts) Now add a uniform magnetic ﬁeld, E, to‘the region with this E ﬁeld in such a
way that the particle travels in a straight line. Evaluate B. l C) (15 pts) Now remove the original E ﬁeld so the particle is traveling only in the B" ﬁeld.
Draw a sketch of the particle’s trajectory, name the trajectory (e.g. straight line, hy
perbola, ellipse, circle, parabola, etc.) and ﬁnd the functional form of y and z for the
trajectory versus X (e.g. 2(13) 2 %x + 3 ). ...
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 Spring '09
 Barnett

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