Download PHY 132–701 - Oakton Community College

PHY 132–701
Oakton Community College
Summer 2012
Practice Test 2
Ten questions
Useful formulas:

F 
Ui 
4 0
r
2
qj
qi
4 0
r
ji
Cseries
R

U total 
C
A
Rseries = R1 + R2
1 nm = 10–9 m
1
4 0
Q
A

V
d
1
1

C1 C2
L
1 q
rˆ
4 0 r 2
ij
  K 0
1

E
q1 q 2
1
qi q j
U
q0
rij
V
0
U
V
1 qq0
4 0 r
1
4 0
Q
r
Q2 1
1
 QV  CV 2
2C 2
2
u
1 2
E
2
P = IV
1
1
1


Rparallel R1 R2
1 µm = 10–6 m
me = 9.11 × 10–31 kg
i j
Qenclosed
Cparallel  C1  C2
U stored 
V = IR

 E  E A 
I  0
V  0
loop
junction
1 pF = 10–12 F
mp = 1.67 × 10–27 kg
 = RC i C 
0 = 8.854 × 10–12 F/m
k
1
4 0
 8.99  10 9
q C
t
e = 1.602 × 10–19 C
Nm2
C2
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PHY 132–701
Oakton Community College
Summer 2012
Practice Test 2
1) In a given x-y plane, a particle q1, with a 20.0 nC charge, sits at the point (0.000 m, 0.400 m). A particle
q2, whose charge is –20.0 nC, sits at (0.300 m, 0.000 m). Give the electric potential (voltage) at the origin
due to these two charges.
2) An electron is accelerated from rest through a potential difference 1200 V. Give the electron’s kinetic
energy after this acceleration a) in electron-volts, b) in joules.
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PHY 132–701
Oakton Community College
Summer 2012
Practice Test 2
3) One proton is held motionless, and another is launched directly at it from a very large distance. If the
initial velocity of the second proton is v1 = 1.00 × 104 m/s, how close does it get to the first?
4) A parallel plate capacitor has plates that are 3.00 mm × 3.00 mm, and a separation of 2.00 µm. What is
its capacitance when the dielectric filling the space between is a) vacuum (K = 1), b) mylar (K = 5.0)?
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PHY 132–701
Oakton Community College
Summer 2012
Practice Test 2
5) For the given configuration of capacitors: a) what is the equivalent capacitance, b) how much charge is
stored on the equivalent capacitance when Vab is 10.0V?
+
3.0 µF
Vab
4.0 µF
2.0 µF
–
–
6) You are given a wire with a diameter d = 5.00 mm and length L =10.0 m. What is the resistance of the
wire if it is made of a) aluminum, Al = 2.75 × 10–8 m, b) copper, Cu = 1.72 × 10–8 m ?
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PHY 132–701
Oakton Community College
Summer 2012
Practice Test 2
7) Find the equivalent resistance for this collection of resistors.
20 
12 
76 
96 
Req
8) In the circuit below, determine how much power is delivered to the 4 k resistor.
2 k
10 V +
–
4 k
2 k
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PHY 132–701
Oakton Community College
Summer 2012
Practice Test 2
9) In the circuit below, determine how much current is flowing through each of the three resistors.
20 k
20 k
2.0 V +
–
+ 5.0 V
20 k
–
10) In the circuit below, the capacitor is initially uncharged, and the switch is closed at t = 0. a) The
moment after the switch is closed, what is the current in the resistor? b) How long does it take for the
resistor current to decrease to half of the value from part a?
t=0
100 k
5.0 V +
–
10.6 µF
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