# Chapter 26 Capacitance and Dieletrics ```1
Chapter 26 Capacitance and Dieletrics
7.
What is the equivalent capacitance of the combination shown?
a.
b.
c.
d.
e.
23.
29 &micro;F
10 &micro;F
40 &micro;F
25 &micro;F
6.0 &micro;F
12 &micro;F
24 &micro;F
20 &micro;F
12 &micro;F
If VA – VB = 50 V, how much energy is stored in the 36-&micro;F capacitor shown?
a.
b.
c.
d.
e.
50 mJ
28 mJ
13 mJ
8.9 mJ
17 mJ
36 &micro;F
A
B
72 &micro;F
54 &micro;F
31.
A 15-&micro;F capacitor and a 30-&micro;F capacitor are connected in series, and this combination is
charged to a potential difference of 50 V. What is the resulting charge on the 30-&micro;F
capacitor?
a. 0.70 mC
b. 0.80 mC
c. 0.50 mC
d. 0.60 mC
e. 0.40 mC
42.
A 200-volt battery is connected to a 0.5-microfarad parallel-plate, air-filled capacitor. Now
the battery is disconnected, with care taken not to discharge the plates. Some Pyrex glass is
then inserted between the plates, completely filling up the space. What is the final
potential difference between the plates? (the dielectric constant for Pyrex is k = 5.6)
Chapter 27 Current and Resistance
1.
14.
A rod of 2.0-m length and a square (2.0 mm x 2.0 mm) cross section is made of a material
with a resistivity of 6.0 x 10–8 Ω ⋅ m. If a potential difference of 0.50 V is placed across the
ends of the rod, at what rate is heat generated in the rod?
a. 3.0 W
b. 5.3 W
c. 8.3 W
d. 1.3 W
e. 17 W
If a mile of 24-gauge copper wire has a resistance of 0.14 kΩ and the resistivity of copper is
1.7 x 10–8 Ω ⋅ m, what is the diameter of the wire? (1 mile = 1.6 km)
a. 0.40 mm
b. 0.50 mm
c. 0.63 mm
d. 0.80 mm
e. 0.25 mm
2
15.
A 50-V potential difference is maintained across a 2.0-m length wire that has a diameter of
0.50 mm. If the wire is made of material that has a resistivity of 7.0 x 10–8 Ω ⋅ m, what is the
current in the wire?
a. 70 A
b. 65 A
c. 61 A
d. 58 A
e. 280 A
Chapter 28 Direct Current Circuits
17.
What is the magnitude of the current in the 20-Ω resistor shown?
10 Ω
a.
b.
c.
d.
e.
20.
+
20 Ω
10 V
15 V
−
−
10 Ω
+
–10 W
+10 W
zero
+20 W
–20 W
−
10 Ω
10 V
20 V
−
+
10 Ω
20 Ω
How many time-constants must elapse if an initially charged capacitor is to discharge 55%
of its stored energy through a resistor?
a.
b.
c.
d.
e.
60.
+
What power is supplied by the 10-V emf shown?
a.
b.
c.
d.
e.
42.
0.75 A
0.00 A
0.25 A
0.50 A
1.00 A
0.60
0.46
0.52
0.40
1.1
If R = 20 Ω, what is the equivalent resistance between points A and B in the figure?
a.
b.
c.
d.
e.
77 Ω
63 Ω
70 Ω
84 Ω
140 Ω
R
2R
4R
R
2R
4R
A
B
```