Magnetic Fields
Practice Test
1.
If the the current in the circuit of Figure 22-5 is 1.5 A, what is the total resistance of the circuit?
a.
16 Ω
b.
8 Ω
c.
18 Ω
d.
4 Ω
Hint
2.
If the charge of an atom's nucleus is +2 and the charge of the surrounding electrons is -2, the atom is __________.
a.
electrically neutral
b.
negatively-charged
c.
unstable
d.
positively-charged
Hint
3.
How does a ground-fault interrupter work?
a.
It detects small differences in current caused by an extra current path and opens the circuit.
b.
It detects small differences in temperatures and opens the circuit.
c.
It detects small differences in voltage caused by an extra voltage path and opens the circuit.
d.
It detects small differences in resistance and opens the circuit.
Hint
4.
Thermal energy is given by:
a.
E
=
I
2
R
b.
E
=
Pt
c.
E
=
P
2
t
d.
E
=
IR
Hint
5.
The direction of the electric field is the direction of the__________.
a.
work done moving the test charge
b.
force on the negative test charge
c.
force on the positive test charge
d.
potential difference
Hint
6.
If a current is traveling toward you in a wire, what is the direction of the magnetic field?
a.
toward you
b.
clockwise
c.
away from you
d.
counterclockwise
Hint
7.
Magnetic domains are __________ in a magnet.
a.
aligned
b.
misaligned
c.
random
d.
scattered
Hint
8.
A positive test charge of 9.0 × 10
-5
" to "9.0×10
-5
C is in an electric field that exerts a force of 3.7×10
-5
N on it. What is the magnitude of the electric field at the location of the test charge?
a.
0.24 N/C
b.
2.4 N/C
c.
4.1 N/C
d.
0.41 N/C
Hint
9.
What is the equation to find current in a series of three resistors?
a.
I
=
V
(
R
1
+
R
2
+
R
3
)
b.
I
=
V
/(
R
1
×
R
2
×
R
3
)
c.
I
=
V
/(
R
1
+
R
2
+
R
3
)
d.
I
=
V
(
R
1
×
R
2
×
R
3
)
Hint
10.
A 75.0 W lightbulb is 25.0% efficient. How many joules of thermal energy does the lightbulb produce each minute?
a.
4500 J
b.
1130 J
c.
563 J
d.
3380 J
Hint
11.
As a positive test charge moves farther from a positive charge in an electric field, the potential energy __________.
a.
increases
b.
decreases
c.
doubles
d.
remains the same
Hint
12.
A voltmeter should be connected to a circuit in __________.
a.
series-parallel
b.
short form
c.
parallel
d.
series
Hint
13.
If you have a 90 V power source with a 30-Ω and 60-Ω resistor in series, what is the voltage drop over the 60-Ω resistor?
a.
60 V
b.
2 V
c.
90 V
d.
30 V
Hint
14.
A positive and a negative charge, each of magnitude 2.7×10
-4
C, are separated by a distance of 10.0 cm. What is the force and direction of the force on each of the particles?
a.
- 6.6×10
4
N, attractive
b.
6.6×10
4
N, repulsive
c.
6.6×10
4
N, attractive
d.
6.6×10
2
N, repulsive
Hint
15.
If current is reduced in an electromagnet, what happens to the magnetic field strength?
a.
it increases
b.
it remains the same
c.
it disappears completely
d.
it is reduced
Hint
16.
An electric field is about 150 N/C downward. What is the direction of the force on a positively-charged particle?
a.
upward
b.
stationary
c.
downward
d.
changes rapidly
Hint
17.
If the resistance of the lightbulb in Figure 22-3 were changed to 6 Ω, what would tha ammeter read?
a.
4 A
b.
6 A
c.
8 A
d.
2 A
Hint
18.
The speed of an electric motor is controlled by varying the __________ through the motor.
a.
voltage
b.
resistance
c.
direction of the north pole
d.
current
Hint
19.
An electron's charge is ________ in magnitude and _________ in sign from a proton's charge.
a.
unequal; opposite
b.
equal; same
c.
equal; opposite
d.
unequal; same
Hint
20.
What are the two kinds of electrical charges?
a.
high and low
b.
static and dynamic
c.
positive and negative
d.
destructive and constructive
Hint
