Quantum Theory
Practice Test
1.
An alternating current source produces changing currents in a wire connected to it. This wire generates electromagnetic fields. What is this wire called?
a.
a polarizer
b.
an oscillator
c.
an antenna
d.
a capacitor
Hint
2.
If Thomson's experiment depicted in Figure 26-1 were done with a proton, how would the magnitude of the
q/m
ratio obtained compare with that for an electron?
a.
It would depend on the velocity of the proton.
b.
It would be more.
c.
It would be less.
d.
It would be the same.
Hint
3.
The ratio of charge stored to electric potential difference is called the __________.
a.
current
b.
capacitance
c.
capacitor
d.
resistance
Hint
4.
Which of the following equations represents the momentum of a photon?
a.
p
=
hf
b.
E
=
mc
2
c.
λ
=
h
/
mv
d.
p
=
h
/
λ
Hint
5.
A proton moves at a speed of 7.9×10
3
m/s as it passes through and is perpendicular to a 0.45-T uniform magnetic field. Find the radius of the circular path.
a.
1.8×10
-4
m
b.
1.0×10
-4
m/s
c.
3.4×10
-3
m
d.
5.6×10
-7
m
Hint
6.
If the combined resistance of the potentiometer and motor in Figure 22-5 is 250 Ω, what is the current through the circuit?
a.
3000 A
b.
48 mA
c.
21 A
d.
120 A
Hint
7.
If the resistance of the lightbulb in Figure 22-3 were changed to 6 Ω, what would tha ammeter read?
a.
6 A
b.
2 A
c.
8 A
d.
4 A
Hint
8.
A negative charge of 1.5×10
-7
C experiences a force of 0.030 N to the right in an electric field. What is the magnitude and direction of the field?
a.
2.0×10
5
N/C directed to the left
b.
4.5x10
-9
N/C directed to the left
c.
4.5×10
-7
N/C directed to the right
d.
2.0×10
5
N/C directed to the right
Hint
9.
A 75.0 W lightbulb is 25.0% efficient. How many joules of thermal energy does the lightbulb produce each minute?
a.
1130 J
b.
4500 J
c.
3380 J
d.
563 J
Hint
10.
Lines drawn to represent an electric field extend __________ a positive charge and __________ a negative charge.
a.
away from, away from
b.
toward, away from
c.
away from, toward
d.
toward, toward
Hint
11.
If a magnetic field points upward and the current is to your left, the force is __________.
a.
away from you
b.
toward you
c.
to your left
d.
to your right
Hint
12.
According to Lenz's law, the resulting force produced by an induced current __________.
a.
opposes the motion of the wire
b.
opposes the current
c.
reduces the resistance
d.
contributes to the motion of the wire
Hint
13.
What is the de Broglie wavelength of an electron moving at 3.0×10
6
m/s?
a.
0.24 m
b.
0.12 nm
c.
0.24 nm
d.
0.49 m
Hint
14.
In the situation depicted in Figure 27-12, if the electron's initial speed is doubled, what stopping potential would be required?
a.
20.0 V
b.
5.0 V
c.
2.5 V
d.
10.0 V
Hint
15.
Electric power is given by:
a.
P
=
VR
b.
P
=
IR
c.
P
=
I
2
R
d.
P
=
V
2
R
Hint
16.
In Figure 21-7b, if both charges were 7.0
μ
C and the left charge were held in place while the right charge were moved from a separation of 0.4 m" to "0.40 m, what would be the magnitude of the difference in the electric potential energy of the system between the initial and final positions?
a.
1.1 J
b.
4.4 J
c.
3.3 J
d.
2.2 J
Hint
17.
The stopping potential,
V
0
, that prevents electrons from flowing across a certain photocell is 6.0 V. What is the kinetic energy in J given to the electrons by the incident light?
a.
6.9×10
-19
J
b.
9.6×10
-19
J
c.
6.4×10
-19
J
d.
1.60×10
-19
J
Hint
18.
Combined electric and magnetic fields that move through space are called __________.
a.
electromagnetic waves
b.
piezoelectric fields
c.
oscillating fields
d.
radiation waves
Hint
19.
Electricity sent over power lines needs __________.
a.
low voltage and low current
b.
high voltage and low current
c.
low voltage and high current
d.
high voltage and high current
Hint
20.
If a current is traveling toward you in a wire, what is the direction of the magnetic field?
a.
counterclockwise
b.
away from you
c.
clockwise
d.
toward you
Hint
