# Capacitance

```Q1) The units of capacitance are equivalent to:
1) J/C
2) V/C
3) J2/C
4) C/J
5) C2/J
Q2) A capacitor C “has a charge Q&quot;. The actual charges on its
plates are:
1) Q, Q
2) Q/2, Q/2
3) Q, -Q
4) Q/2, -Q/2
5) Q, 0
Q3) Does the capacitance C of a capacitor increase, decrease, or
remain the same (a) when the charge q on it is doubled and
(b) when the potential difference V across it is tripled?
1) (a) increase (b) increase
2) (a) increase (b) decrease
3) (a) increase (b) remain the same
4) none of the above
Q4) If the charge on a parallel-plate capacitor is doubled:
1) the capacitance is halved
2) the capacitance is doubled
3) the electric field is halved
4) the electric field is doubled
5) the surface charge density is not changed on either plate
Q5) The magnitude of the charge on the plates of an isolated
parallel plate capacitor is doubled. Which one of the following
statements is true concerning the capacitance of this parallel-plate
system?
1) The capacitance is decreased to one half of its original value.
2) The capacitance is increased to twice its original value.
3) The capacitance remains unchanged.
4) The capacitance depends on the electric field between the plates.
5) The capacitance depends on the potential difference across the
plates.
Q6) The capacitance of a parallel-plate capacitor can be increased
by:
1) increasing the charge
2) decreasing the charge
3) increasing the plate separation
4) decreasing the plate separation
5) decreasing the plate area
Q7) Pulling the plates of an isolated charged capacitor apart:
1) increases the capacitance
2) increases the potential difference
3) does not affect the potential difference
4) decreases the potential difference
5) does not affect the capacitance
Q8) A parallel-plate capacitor has square plates of edge length L,
separated by a distance d. A second capacitor is made with L
doubled and d decreased by a factor of 2. By what factor is the
capacitance of the new capacitor increased?
1) 1
2) 2
3) 4
4) 16
5) None of these.
L
L
d
Q9) A parallel plate capacitor is charged by connecting it to a 12 V
battery. After the plates are charged, the capacitor is disconnected
from the battery. If the plates of the capacitor are then pulled apart,
the
1) potential difference between the plates increases
2) potential difference between the plates decreases
3) magnitude of the charge on each plate increases
4) magnitude of the charge on each plate decreases
5) none of the above
Q10) A parallel plate capacitor is charged by connecting it to a 12
V battery. If the plates of the capacitor are the pulled apart while
the capacitor is still connected to the battery, the
1) potential difference between the plates increases
2) potential difference between the plates decreases
3) magnitude of the charge on each plate increases
4) magnitude of the charge on each plate decreases
5) two of the above
Q11) Consider a capacitor made of two isolated parallel metal
plates separated by a distance d. The top plate is positively
charged with total charge +Q; the bottom plate is negatively
charged with total charge –Q. A slab of metal of thickness t &lt; d is
inserted between the plates, not connected to either one. Upon
insertion of the metal slab, the voltage difference between the top
and bottom plates.
1) increases
2) decreases
3) remains constant.
Q12) The figure below shows three circuits, each consisting of a
switch and two capacitors, initially charged as indicated. After the
switched have been closed, in which circuit (if any) will the charge on
the left-hand capacitor (a) increase (b) decreases, and (c) remain the
same?
1) (a) 3 (b) 1 (c) 2
2) (a) 1 (b) 3 (c) 2
3) (a) 2 (b) 1 (c) 3
4) (a) 3 (b) 2 (c) 1
5) (a) 2 (b) 3 (c) 1
Q13) Two capacitors are connected in parallel:
1) They both have the same voltages across their terminals
2) They both have the same charges on their plates
3) Both the voltages and charges can differ depending upon their
capacitances
4) Both the voltages and charges are the same independent of their
capacitances
Q14) Two capacitors are connected in series:
1) They both have the same voltages across their terminals
2) They both have the same charges on their plates
3) Both the voltages and charges can differ depending upon their
capacitances
4) Both the voltages and charges are the same independent of their
capacitances
Q15) Two capacitors C1 and C2 are hooked in series. The
equivalent series capacitance of the two capacitors is …
1) Always less than C1 or C2
2) Always greater than C1+C2
3) Always greater than C1 or C2 but always less than C1+C2
4) None of these.
Q16) For each
circuit in the figure,
are the capacitors
connected in series,
parallel, or neither?
1) (a) series (b) parallel
2) (a) series (b) parallel
3) (a) series (b) neither
4) (a) series (b) neither
5) (a) parallel (b) parallel
(c) parallel
(c) neither
(c) parallel
(c) neither
(c) parallel
Q17) A 2-F and a 1-F capacitor are connected in series and a
potential difference is applied across the combination. The 2-F
capacitor has:
1) twice the charge of the 1-F capacitor
2) half the charge of the 1-F capacitor
3) twice the potential difference of the 1-F capacitor
4) half the potential difference of the 1-F capacitor
5) none of the above
Q18) A 2-F and a 1-F capacitor are connected in parallel and a
potential difference is applied across the combination. The 2-F
capacitor has:
1) twice the charge of the 1-F capacitor
2) half the charge of the 1-F capacitor
3) twice the potential difference of the 1-F capacitor
4) half the potential difference of the 1-F capacitor
5) none of the above
Q19) Two identical capacitors are connected in series and two,
each identical to the first, are connected in parallel. The equivalent
capacitance of the series connection is the equivalent capacitance
of parallel connection.
1) twice
2) four times
3) half
4) one-fourth
5) the same as
Q20) How many different capacitances can you produce using
three different capacitors if you have all three connected in the
circuit each time?
1) 5
2) 6
3) 7
4) 8
5) 9
Q21) Determine the equivalent capacitance in pF for the network
shown when C = 12 pF.
1) 48
2) 12
3) 24
4) 6.0
5) 59
C
C
C
2C
Q22) What is the equivalent capacitance in F of the combination
shown?
1) 20
2) 10
3) 40
4) 25
5) 6.0
12  F
24  F
20  F
12  F
Q23) Consider two capacitors, each having plate separation d. In
each case, a slab of metal of thickness d/3 is inserted between the
plates. In case (a), the slab is not connected to either plate. In case
(b), it is connected to the upper plate. The capacitance is higher for
1) case (a).
2) case (b).
3) The two capacitances are equal.
Q24) Consider a simple parallel-plate capacitor whose plates are
given equal and opposite charges and are separated by a distance d.
Suppose the plates are pulled apart until they are separated by a
distance D &gt; d. The electrostatic energy stored in the capacitor is
1) greater than
2) the same as
3) smaller than
before the plates were pulled apart.
Q25) A parallel-plate capacitor is charged up (+Q on one plate, -Q
on the other). The plates are isolated so the charge Q cannot
change. The plates are then pulled apart so that the plate
separation d increases. The total electrostatic energy stored in the
capacitor
1) increases
2) decreases
3) remains constant.
+++++++++++++ +
-------------------
Q26) A parallel plate capacitor is attached to a battery which
maintains a constant voltage difference V between the capacitor
plates. While the battery is attached, the plates are pulled apart so
their separation increases. The electrostatic energy stored in the
capacitor
1) increases
2) decreases
3) stays constant.
V
+++++++++++++ +
-------------------
Q27) Two parallel plate capacitors have the same areas and
distances between the plates. Capacitor A has air between the
plates while capacitor B has paper separating the plates. Which
capacitor can store a greater charge?
1) Capacitor A
2) Capacitor B
3) They can both store the same amount.
Q28) A parallel-plate capacitor is attached to a battery that
maintains a constant potential difference V between the plates.
While the battery is still connected, a glass slab is inserted so as to
just fill the space between the plates. The stored energy
1) increases.
2) decreases.
3) remains the same.
Q29) Which one of the following changes will necessarily increase
the capacitance of a capacitor?
1) decreasing the charge on the plates
2) increasing the charge on the plates
3) placing a dielectric between the plates
4) increasing the potential difference between the plates
5) decreasing the potential difference between the plates
Q30) Complete the following statement: When a dielectric with
constant κ is inserted between the plates of a charged isolated
capacitor
1) the capacitance is reduced by a factor κ.
2) the charge on the plates is reduced by a factor of κ.
3) the charge on the plates is increased by a factor of κ.
4) the electric field between the plates is reduced by a factor of κ.
5) the potential difference between the plates is increased by a
factor of κ.
Q31) A parallel plate capacitor is fully charged at a potential V. A
dielectric with constant κ = 4 is inserted between the plates of the
capacitor while the potential difference between the plates
remains constant. Which one of the following statements is false
concerning this situation?
1) The energy density remains unchanged.
2) The capacitance increases by a factor of four.
3) The stored energy increases by a factor of four.
4) The charge on the capacitor increases by a factor of four.
5) The E-field between the plates increases by a factor of four.
Q32) A parallel-plate capacitor with a dielectric between the plates
is charged so that +Q resides on one plate, –Q on the other. With
the plates isolated and the charge Q constant, the dielectric is
pulled out from between the plates. The energy stored in the
capacitor ...
1) increases
2) decreases
3) stays the same.
Q33) A dielectric is inserted between the plates of a capacitor. The
system is then charged and the dielectric is removed. The
electrostatic energy stored in the capacitor is
1) greater than
2) the same as
3) smaller than
it would have been if the dielectric were left in place.
Q34) An air filled parallel-plate capacitor has a capacitance of 1.0
pF. The plate separation is then doubled and a wax dielectric is
inserted. As a result, the capacitance becomes 2.0 pF. The
dielectric constant of the wax is:
1) 0.25
2) 0.5
3) 2.0
4) 4.0
5) 8.0
Q35) A parallel-plate capacitor with a dielectric between the plates
is charged so that +Q resides on one plate, –Q on the other. The
capacitor is hooked to a battery which maintains a constant voltage
between the plates as the dielectric is removed. The energy stored
in the capacitor ...
1) increases
2) decreases
3) stayed the same.
Q36) With the voltage fixed, as the slab is removed, the charge Q
on the capacitor ..
+Q
1) increases
2) decreases
3) remains the same
V
-Q
Q37) A capacitor with capacitance C is connected to a battery until
charged, then disconnected from the battery. A dielectric having
constant κ is inserted in the capacitor. What changes occur in the
charge, potential and stored energy of the capacitor after the
dielectric is inserted?
1) V stays same, Q increases, U increases
2) V stays same, Q decreases, U stays same
3) increases, Q decreases, U increases
4) V decreases, Q stays same, U decreases
5) None of the above
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