Practice Exam 3
PHY 2140
1. A 10.0 F capacitor and a 2.00 H inductor are connected in series with a 60.0 Hz source
whose rms output is 150 V. What is the value of the rms current in the circuit?
a.
b.
c.
d.
e.
0.199 A
205 mA
0.307 A
566 mA
147 mA
2. A step-up transformer is designed to have an output voltage of 5500 V (rms) when the
primary is connected across a 110 V (rms) source. If there are 100 turns on the primary
winding, how many turns are required on the secondary winding?
a.
b.
c.
d.
e.
50
1500
3500
5000
5500
3. An electromagnetic wave in vacuum has a magnetic field amplitude of 7.00 x 10-7 T. What
is the amplitude of the corresponding electric field?
a.
b.
c.
d.
e.
210 V/m
320 V/m
430 V/m
540 V/m
650 V/m
NAME
4. An electron has a speed of v = 0.90c. At what speed will a proton have a momentum equal
to that of the electron?
a.
b.
c.
d.
e.
1.1 x 104 m/s
2.4 x 104 m/s
2.1 x 105 m/s
3.4 x 105 m/s
4.8 x 106 m/s
5. In a certain x-ray machine electrons are accelerated through a potential difference of 2 MeV
before striking a metal target. With what speed do the electrons strike the x-ray target?
a.
b.
c.
d.
e.
0.272c
0.642c
0.867c
0.979c
2.79c
6. A muon formed high in Earth’s atmosphere travels at a speed v = 0.99c for a distance of
4.6 km before it decays. How long does the muon live, as measured in its reference frame?
a.
b.
c.
d.
e.
zero
2.2 s
11 s
15 s
110 s
NAME
7. What is the minimum accelerating voltage required to produce an x-ray with a wavelength
of 0.0300 nm?
a.
b.
c.
d.
e.
6.63 V
13.8 V
19.9 kV
41.4 kV
62.5 MV
8. Assuming that the tungsten filament of a lightbulb is a blackbody, what is its peak
wavelength if its temperature is 2900 K?
a.
b.
c.
d.
e.
99.9 pm
99.9 m
999 nm
9.99 mm
99.9 m
9. A radio wave has a wavelength of 6 m. What is the frequency of this radio wave?
a.
b.
c.
d.
e.
5 Hz
10 kHz
50 MHz
100 MHz
500 MHz
10. What is the energy in electron volts of a photon having a wavelength of 5.00 cm?
a.
b.
c.
d.
e.
3.98 x 10-7 eV
2.49 x 10-5 eV
7.96 x 10-3 eV
3.17 eV
66.3 eV
NAME
11. What is the value the inductor which must be inserted in a 60 Hz circuit in series with a
generator of 170 V maximum output voltage to produce an rms current output of 0.75 A?
12. The proper length of one spaceship is three times that of another. The two spaceships are
traveling in the same direction and, while both pass directly overhead, an observer on Earth
measures the two spaceships to be the same length. If the slower ship is moving with a
speed of 0.350c, determine the speed of the faster spaceship.
I rms 
I max
2
Vrms 
VR ,rms  I rms R
Vmax
VC ,rms  I rms X C
2
XC 
VL , rms  I rms X L
Z  R2  X L  X C 
2
V  IZ
tan  
1
2 f C
X L  2fL
XL  XC
R
Pav  I rms Vrms cos 
E
c
B
c  f
L  LP 
p  mv
KE  mc 2  mc 2
E 2  p 2c2  m2c4
En  nhf
KEmax  hf  
maxT  0.2898 102 m  K
h
h
 
p mv
h
xp 
4
h
E t 
4
melectron = 9.11 x 10-31 Kg
mproton = 1.67 x 10-27 Kg
For an electron: mec2=511 keV
c = 3.00 x 108 m/s
h = 6.63 x 10-34 J∙s
e = 1.6 x 10-19 C
f 
1
2 LC
t  t P
E  mc 2
Power Prefix Symbol
10-12
picop
10-9 nanon
-6
10 micro
-3
10
millim
10-2 centic
3
10
kilok
106 megaM
109
gigaG
 
v AB 
1
1  v2 c2
v AC  vCB
v v
1  AC 2 CB
c
min 
hc
eV
2d sin   m
( m  1, 2,3, )
    0
h
(1  cos  )
me c
hc
E

1 eV = 1.6 x 10-19 J
