Section 21.2
Applications of Electric Fields
Practice Test
1.
Both a 1.2-
μ
F and a 5.5-
μ
F capacitor are connected across an 11-V electric potential difference. Which capacitor has the greater charge and what is it?
a.
1.2
μ
F; 1.3×10
-5
C
b.
5.5
μ
F; 6.1×10
-5
C
c.
1.2
μ
F; 6.1×10
-5
C
d.
5.5
&mu
F; 1.3×10
-5
C
Hint
2.
If 2.0×10
2
J of work are performed to move one coulomb of charge from a positive plate to a negative plate, what potential difference exists between the plates?
a.
5.0×10
-3
V
b.
2.0×10
3
V
c.
2.0×10
2
V
d.
1.6×10
-19
V
Hint
3.
The ratio of charge stored to electric potential difference is called the __________.
a.
capacitance
b.
current
c.
capacitor
d.
resistance
Hint
4.
What electric potential difference is applied to two metal plates 0.350 m apart if the electric field between them is 3.75×10
3
N/C?
a.
1.31×10
0
V
b.
1.31×10
3
V
c.
1.07×10
3
V
d.
1.07×10
4
V
Hint
5.
The electric field intensity between two large, charged, parallel metal plates is 6500 N/C. The plates are 12 cm apart. What is the electric potential difference between them?
a.
7.8×10
4
V
b.
7.8×10
2
V
c.
7.8×10
5
V
d.
7.8×10
-2
V
Hint
6.
In the set-up of Figure 21-9, if a drop is moving down with a constant speed, then ___.
a.
the gravitational force on the drop must be equal to the electric force on the drop
b.
the gravitational force on the drop must be greater than the electric force on the drop
c.
the upper plate must be negatively charged
d.
the lower plate must be negatively charged
Hint
7.
Two parallel plates are given opposite charges. A voltmeter measures the electric potential difference to be 47.0 V. The plates are 5.0 cm apart. What is the magnitude of the electric field between them?
a.
1.1×10
-3
N/C
b.
1.1×10
-4
N/C
c.
9.4×10
3
N/C
d.
9.4×10
2
N/C
Hint
8.
Electric potential difference is measured in __________.
a.
newtons per coulomb
b.
coulombs per joule
c.
joules per coulomb
d.
volts per coulomb
Hint
9.
Touching a body to Earth to eliminate excess charge is called __________.
a.
resistance
b.
capacitance
c.
static
d.
grounding
Hint
10.
In the set-up of Figure 21-9, if a drop is moving up with a constant speed, then ___.
a.
the upper plate must be negatively charged
b.
the gravitational force on the drop must be equal to the electric force on the drop
c.
the gravitational force on the drop must be less than the electric force on the drop
d.
the lower plate must be negatively charged
Hint
11.
A 6.4-
μ
F capacitor is first charged so that the electric potential difference is 5.0 V. How much additional charge is needed to increase the electric potential difference to 12.0 V?
a.
7.7×10
-5
C
b.
4.5×10
-5
C
c.
7.7×10
5
C
d.
4.5×10
5
C
Hint
12.
A voltmeter reads 450 V across two charged, parallel plates that are 5.0 cm apart. What is the electric field between them?
a.
9.0×10
2
N/C
b.
1.1×10
-4
N/C
c.
9.0×10
3
N/C
d.
9.0×10
1
N/C
Hint
13.
The SI derived unit of potential difference is the __________.
a.
coulomb
b.
joule
c.
volt
d.
ohm
Hint
14.
As a positive test charge moves farther from a positive charge in an electric field, the potential energy __________.
a.
decreases
b.
doubles
c.
increases
d.
remains the same
Hint
15.
In the set-up of Figure 21-9, if the electric force up on a drop equals the gravitational force down on the drop, the drop ___.
a.
will accelerate down
b.
must be stationary
c.
will accelerate up
d.
could move upward at constant speed
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, how much work would be done on the system?
a.
1.1 J
b.
-1.1 J
c.
2.2 J
d.
-2.2 J
Hint
17.
In a Millikan oil drop experiment, a drop has been found to weigh 1.92×10
-14
N. When the electric field is 3.0×10
4
N/C, the drop is suspended motionless. What is the charge on the oil drop?
a.
5.8×10
-19
C
b.
6.4×10
-19
C
c.
6.4×10
19
C
d.
5.8×10
-10
C
Hint
18.
A 35-
μ
F capacitor has an electric potential difference of 50.0 V across it. What is the charge on the capacitor?
a.
1.4×10
-6
C
b.
1.75×10
-0
C
c.
1.8×10
3
C
d.
1.8×10
-3
C
Hint
19.
When the electric potential difference between two positions in an electric field is zero, the positions are __________.
a.
polar
b.
at equipotential
c.
close together
d.
in equilibrium
Hint
20.
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.
3.3 J
b.
1.1 J
c.
4.4 J
d.
2.2 J
Hint
21.
The direction of the electric field is the direction of the__________.
a.
force on the negative test charge
b.
work done moving the test charge
c.
force on the positive test charge
d.
potential difference
Hint
22.
What work is done when 3.5 C is moved through an electric potential difference of 4.5 V?
a.
-1.6×10
1
J
b.
7.8× 10
1
J
c.
1.6×10
1
J
d.
1.6×10
1
J/C
Hint
