Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)
For two capacitors in series, if one capacitance is much larger than the other, the total capacitance is
1)
A)
approximately equal to the capacitance of the larger capacitor.
B)
approximately equal to the capacitance of the smaller capacitor.
C)
approximately equal to the product of the capacitances.
D)
No approximation is possible
2)
An ideal capacitor
2)
A)
stores energy.
B)
radiates energy.
C)
dissipates energy.
D)
All of the above
3)
For two capacitors in parallel, if one capacitance is much larger than the other, the total capacitance
is
3)
A)
approximately equal to the product of the capacitances.
B)
approximately equal to the capacitance of the smaller capacitor.
C)
approximately equal to the capacitance of the larger capacitor.
D)
No approximation is possible
4)
The breakdown voltage specification of acapacitor is the voltage at which
4)
A)
the attraction between the capacitor plates pulls them together and the capacitor plates short
out.
B)
the dielectric between the plates can begin to conduct current.
C)
the outer case insulation around the capacitor fails.
D)
None of the above
5)
The total capacitance of two capacitors, 2 µF and 10 µF, in series, is
5)
A)
1.59 µF
B)
1.67 µF
C)
20 µF
D)
12 µF
6)
1 F of capacitance is defined as
6)
A)
1 V of voltage per coulomb.
B)
1 C of charge per volt.
C)
1 A of current per ohm.
D)
1 V of voltage per ohm.
B
7)
Acapacitor opposes an instantaneous change of
7)
A)
current.
B)
voltage.
C)
resistance.
D)
None of the above
B
8)
Current can flow into and out of acapacitor
8)
A)
only when the circuit reaches steady–state.
B)
only during the transient.
C)
only at t = 0.
D)
never, because the capacitor is an open circuit.
B
9)
The capacitance of aparallel–plate capacitor is inversely proportional to
9)
A)
the separation between the plates.
B)
the dielectric constant.
C)
the plate area.
D)
None of the above
A
B
10)
The dipoles in adielectric material set up an electric field which
10)
A)
assiststhe electric field due to the charge on the plates.
B)
does not have any electric field effect.
C)
opposes the electric field due to the charge on the plates.
D)
None of the above
11)
When aDC voltage source is switched on in acircuit with resistance and capacitance, the voltages
and currents across the components
11)
A)
jump to the DC steady–state values immediately.
B)
are indeterminate because the capacitor is an open.
C)
go through atransient to reach the DC steady–state values.
D)
stay at zero because the capacitor is an open.
12)
The leakage resistance of acapacitor is important when
12)
A)
the dielectric leaks out of the capacitor.
B)
the leakage resistance is not much greater than other resistances in the circuit.
C)
the leakage resistance is much greater than other resistances in the circuit.
D)
the wire resistance on the capacitor leads is significant.
13)
The effect of acapacitor on the AC voltage across and current through the capacitor is that
13)
A)
the voltage and the current are in–phase.
B)
the current leads the voltage by 90°.
C)
the voltage leads the current by 90°.
D)
the voltage and current are 180°out–of–phase.
14)
The total capacitance of two capacitors, 2 µF and 10 µF, in parallel, is
14)
A)
1.59 µF
B)
12 µF
C)
1.67 µF
D)
20 µF
15)
Acapacitor can
15)
A)
store electrical energy.
B)
return electrical energy to acircuit.
C)
Both Aand B
D)
Neither Anor B
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
16)
The capacitance of aparallel plate capacitor with adielectric that has arelative dielectric
constant of 5, aplate area of 8in2,and aplate separation of 0.03 mm is ________ (give
number and units).
16)
17)
The total capacitance of three capacitors, 1 µF, 2 µF, and 2.2 µF in series is ________ (give
number and units).
17)
18)
The capacitance of aparallel plate capacitor with adielectric that has arelative dielectric
constant of 2.1, aplate area of 100cm2,and aplate separation of 0.05 mm is ________ (give
number and units).
18)
19)
The total capacitance of two series capacitors, 5µFand 2µF,that are in parallel with a 1 µF
capacitor is ________ (give number and units).
19)
20)
The total capacitance of three capacitors, 1µF, 2 µF,and 2.2 µF in parallel is ________ (give
number and units).
20)
21)
The total capacitance of two parallel capacitors, 1µF and 2µF,that are in series with a 5 µF
capacitor is ________ (give number and units).
21)
22)
The energy stored in a 2 µF capacitor if 10 Vis applied is ________ (give number and units).
22)
23)
The plate area in cm2required for aparallel plate capacitor to have acapacitance of 0.01
µF, if the dielectric has arelative permittivity of 5and aplate separation of 0.03 mm, is
________ (give number and units).
23)
24)
The capacitance of Nidentical series capacitors of capacitance Ceach is ________.
24)
25)
The capacitance of Nidentical parallel capacitors of capacitance Ceach is ________.
25)
26)
The dielectric constant and the permittivity are the same quantity.
26)
27)
The relative permittivity is sometimes called the dielectric constant, but it is really the relative
dielectric constant.
27)
28)
The capacitances of capacitors in series add.
28)
29)
Acapacitor is astructure that can store separated charge.
29)
30)
The capacitance of aparallel plate capacitor is directly proportional to the plate area.
30)
31)
The capacitances of capacitors in parallel add.
31)
32)
Unlike charges repel, and like charges attract.
32)
33)
The relative permittivity is the factor by which the permittivity of vacuum is greater than the
permittivity of adielectric material.
33)
34)
The dielectric constant of mica is greater than the dielectric constant of air.
34)
35)
A voltage cannot exist between separated charge.
35)
36)
An electric field exists between separated positive and negative charges.
36)
37)
The capacitance of aparallel plate capacitor is directly proportional to the permittivity.
37)
38)
The capacitance of aparallel plate capacitor is directly proportional to the separation between the
plates.
38)
39)
Capacitors oppose an instantaneous change in current.
39)
40)
Capacitors store electrical energy in an electric field.
40)
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
41)
Describe the difference between aresistor and acapacitor from an energy viewpoint.
41)
42)
Describe why adielectric increases capacitance.
42)
43)
Describe why acapacitor opposes an instantaneous change of voltage.
43)
44)
Describe (and/or sketch) and explain the curve of the voltage versus time when DC is
applied to acircuit with resistance and capacitance.
44)
45)
Identify and explain the phase shift between the AC voltage across and the AC current
through acapacitor.
45)
Answer Key
Testname: C5
8
Answer Key
Testname: C5
9