Download Capacitor

AL-MC-Capacitor / p.1
1.
(88-I-34)
A parallel-plate capacitor is charged by a battery
A.
40 V.
and the energy stored in the capacitor is E. The
B.
56 V.
connections to the battery are then removed. If one
C.
60 V.
of the plates is moved so that the plate-separation
D.
64 V.
is halved, the electrical energy stored in the
E.
70 V.
capacitor will
4.
A.
B.
2.
(90-I-30)
1
E.
4
1
E.
decrease to
2
decrease to
C.
remain the same.
A parallel-plate capacitor is connected to a battery
D.
increase to 2 E.
as shown. What will happen if the separation of the
E.
increase to 4 E.
plates is increased?
(88-I-35)
capacitance
Using the vibrating reed switch S, in the above
voltage
charge
A.
decreases decreases
decreases
B.
decreases unchanged
C.
decreases decreases
D.
increases
unchanged
decreases
E.
increases
unchanged
increases
decreases
increases
circuit, the capacitor C is charged from battery B
and completely discharged through the resistor R
5.
(91-I-33)
with a frequency of 25 Hz. When a CRO is
connected across R, the waveform will look like :
Circuit A
Circuit B
Three identical capacitors are connected to the
same d.c. source in series (circuit A) and then in
parallel (circuit B). The magnitude of the ratio of
the total energies stored by the capacitors in circuit
A to circuit B is
3.
(89-I-27)
A.
1/9
A capacitor is charged to a p.d. of 100 V and then
B.
1/3
connected across a resistor. After 1 s, the p.d.
C.
1
across the capacitor is 80 V. After another second,
D.
3
the p.d. across the capacitor will be
E.
9
AL-MC-Capacitor / p.2
6.
(91-I-41)
In the above circuit, the a.c. source has a r.m.s.
voltage of 5.0 V alternating at 50 Hz. What is the
r.m.s. current?
A.
0.033  A
A parallel-plate capacitor is connected to a battery
B.
0.12  A
as shown. What will happen if the separation of the
C.
0.21 mA
plates is increased?
D.
120 mA
E.
210 mA
capacitance
voltage
charge
9.
A.
decreases
decreases
B.
decreases
unchanged
(93-I-30)
decreases
decreases
C.
decreases
decreases
D.
increases
unchanged
increases
An initially uncharged capacitor of capacitance C
decreases
E.
increases
is connected in series with a resistor R and a
unchanged
battery of e.m.f. E. What will be (1) the total work
increases
done by the battery in fully charging up C and (2)
the energy finally stored in C?
7.
(92-I-28)
Work done by
battery
1/2 CE
A.
D.
E.
the current is kept constant at 20  A by
continuous adjustment of R. During this period, the
p.d. across the capacitor has fallen by
8.
10.
2
CE
2
1/2 CE
CE 2
CE 2
C.
connected in the circuit above. For a period of 40 s,
in C
0
2
B.
A charged capacitor C, of 10  F capacitance, is
Energy stored
0
1/2 CE
2
1/2 CE
2
CE 2
(94-IIA-28)
A parallel-plate capacitor of capacitance
Co is
A.
8.0  10-4 V
formed by two rectangular metal plates having
B.
1.3  10 V
separation d. Now each of the plates is cut into two
C.
14 V
smaller, identical ones to form two capacitors, each
D.
20 V
with plate separation 2d. What is the capacitance
E.
80 V
when they are connected in parallel?
(92-I-41)
-2
A.
1/2 Co
B.
1/4 Co
C.
Co
AL-MC-Capacitor / p.3
11.
D.
2 Co
E.
4 Co
(94-IIA-30)
In the above circuit, a charged capacitor
C1 is
connected across AB so that it is parallel with two
initially uncharged capacitors
C2 and C3 . Which
of the following statements is/are correct when
switch S is closed?
(1)
The potential difference across AB will drop.
(2)
The combined capacitance across AB will
A parallel-plate capacitor is charged by a constant
increase.
voltage source. With the plates remaining
(3)
The quantity charge on
C2 is the same as
13.
(96-IIA-21)
connected to the source, the plate separation, d, is
then gradually increased from an initial value
that on
C3 .
d0 .
Which of the following graphs best shows the
relationship between the energy, U, stored in the
12.
A.
(1) only
B.
(3) only
C.
(1) and (2) only
D.
(2) and (3) only
E.
(1), (2) and (3)
(95-IIA-40)
A capacitor C and an inductor L with some
resistance are connected to a battery as shown in the
figure. When switch S is moved from A to B, what
is the trace observed on the screen of the CRO with
the time base on?
capacitor and plate separation, d?
AL-MC-Capacitor / p.4
14.
15.
(96-IIA-22)
A.
+40  C
A charged capacitor is connected across a resistor.
B.
+80  C
Its voltage drops to one-third of the original value
C.
0 C
in 10 s. Find the time constant of the circuit.
D.
-80  C
E.
-40  C
A.
4.1 s
B.
9.1 s
C.
11 s
D.
25 s
E.
30 s
17.
(98-IIA-23)
(97-IIA-24)
A variable capacitor can be used
(1)
as the volume control of an amplifier.
(2)
To tune a radio to receive a certain channel.
(3)
To change the power factor of an a.c. circuit.
A changing voltage V is applied across AB in the
16.
A.
(1) only
B.
(3) only
C.
(1) and (2) only
across the capacitor is found to vary with time t as
D.
(2) and (3) only
shown. Which of the following graphs shows the
E.
(1), (2) and (3)
(97-IIA-30)
variation of potential difference
resistor R with time t?
In the above circuit, the cell has e.m.f. 6 V and
negligible internal resistance. The resistances of
the four resistors
Circuit shown. The potential difference
R1 , R2 , R3 and R4 are
6  , 3  , 1  and 2  respectively. The
capacitor has capacitance 20 F . At steady state,
the charge on the capacitor plate connecting to A is
V AC
VR across the
AL-MC-Capacitor / p.5
18.
(98-IIA-24)
20.
(99-IIA-22)
A charged capacitor of capacitance 47 F is
connected to a voltmeter. The voltmeter reading
drops from 8 V to 2 V in 7.8s. Find the resistance
of the voltmeter.
A charged capacitor
C1 , is connected to an
uncharged capacitor
C2 of larger capacitance
through a resistor R as shown above. When switch
A.
60 k
B.
80 k
C.
120 k
D.
166 k
E.
240 k
S is closed, which of the following statements is
INCORRECT?
A.
21.
(99-IIA-24)
The total charges on the two capacitors
remain unchanged.
B.
The final charge on
than that on
C.
C2 is greater
C1 .
The potential difference across
C1
falls.
D.
E.
19.
A.
5V
The total energy stored in the two
B.
15 V
capacitors remains the same.
C.
30 V
D.
36 V
E.
40 V
the following deductions must be correct?
It stores 1 coulomb of charge at a potential
difference of 1 volt.
It gains 1 joule of electrical energy when it
has 1 coulomb of charge.
(3)
output is
capacitors finally becomes equal.
A capacitor has a capacitance of 1 farad. Which of
(2)
as shown in the above circuit. The voltage at the
The potential difference across the two
(98-IIA-29)
(1)
Three capacitors are connected to a 45 V supply
It will be fully charged in 1 second by a
constant current of 1 ampere.
A.
(1) only
B.
(3) only
C.
(1) and (2) only
D.
(2) and (3) only
E.
(1), (2) and (3)
AL-MC-Capacitor / p.6
22.
(99-IIA-25)
24.
(00-IIA-30)
A capacitor is charged by a constant current.
Which of the following graphs shows the time
variation of the energy stored in the capacitor
during the charging process?
In the above circuit, the battery has an e.m.f. of
6.0V and all the capacitors are identical. Initially
none of the capacitors are charged. The switch is
first connected to X and then to Y. What is the final
potential difference between Z and Y?
23.
(99-IIA-26)
25.
A.
1.0 V
B.
1.5 V
C.
2.0 V
D.
2.4 V
E.
3.6 V
(01-IIA-23)
The two plates of a parallel-plate capacitor initially
carry equal amounts of positive charge. If some
charges are transferred from one plate to another,
the charges on the plates are respectively
+900  C and +100  C. The potential difference
across the plates becomes 4 V. what is the
In the above circuit, a capacitor is charged from a
capacitance of the capacitor?
battery E and then completely discharged through a
resistor R using a vibrating reed switch S. The
waveform displayed on the screen of the CRO with
suitable time base should be
A.
25  F
B.
100  F
C.
125  F
D.
200  F
E.
225  F
AL-MC-Capacitor / p.7
26.
(01-IIA-24)
29.
(02-IIA-23)
A ‘jumbo’ capacitor has capacitor 100 000  F.
Such a capacitor charged to 20 V would
(1)
provide a mean current of 1 mA for 2000s.
(2)
be completely discharged through a 10 
resistor in 1 s.
(3)
store 40 J of electrostatic energy.
A parallel-plate capacitor is first charged by
connecting it to a battery. After disconnecting the
A.
(1) only
battery, one of the plates of the capacitor is shifted
B.
(3) only
upward slightly as shown. What would happen to
C.
(1) and (2) only
each of the following quantities
D.
(2) and (3) only
E.
(1), (2) and (3)
V: the potential difference between the plates
Q: the magnetic of the charge on each plate
27.
(01-IIA-25)
C: the capacitance of the capacitor
If the separation between the plates of a
parallel-plate capacitor is increased by 20%, its
V
capacitance will
Q
C
A.
decreased unchanged increased
B.
unchanged decreased decreased
A.
decrease by 17%
C.
increased
decreased decreased
B.
increase by 17%
D.
increased
unchanged decreased
C.
decrease by 20 %
D.
increase by 20 %
E.
decrease by 25 %
30.
(02-IIA-26)
A capacitor is discharged through a resistance of 1
k  . If the time constant of the discharging circuit
28.
(02-IIA-22)
is 2 ms, what is the capacitance of the capacitor?
Three identical capacitors, each of capacitance C,
from a network as shown. What is the equivalent
capacitance between terminals X and Y?
A.
B.
C.
D.
C
3
C
2
2
C
3
3C
A.
0.5 F
B.
1 F
C.
2 F
D.
5 F
AL-MC-Capacitor / p.8
31.
(03-IIB-26)
33.
(03-IB-29)
A capacitor is first charged by a battery and then
discharged through a resistor. The experiment is
then repeated, but this time with a resistor of twice
the resistance value. Which statement about the
second experiment as compared to the first is
correct?
In the figure, A is an earthed metal plated while B
A.
is a positively charged metal plate parallel to A.
The separation between the plates is much less
B.
than the length of each plate. If A is moved closer
to B, what would happen to the electric potential of
C.
B and the electric field strenght between the plates?
(Induced charges are not indicated.)
D.
Electric potential of B Electric field strength
32.
A.
increase
increase
B.
increase
remain unchanged
C.
decrease
decrease
D.
decrease
remain unchanged
34.
The initial current through the resistor is
doubled.
The energy dissipated in the resistor is
doubled.
The total charge flowing through the
resistor is doubled.
The time for the capacitor to lose half of
its charge id doubled.
(04-IIA-17)
(03-IIB-28)
A parallel-plate capacitor with plates A and B is
connected to a battery as shown. Pate A is earthed.
P is a point between the plates. If plate B is shifted
upwards slightly to position B’ while the capacitor
In the circuit, the battery has constant e.m.f. 6V
remains connected to the battery, what would
and negligible internal resistance. Initially switch
happen to each of the following physical
K is open. Switch K is then closed and after some
quantities?
time a steady state is reached. The charges passing
E: the electric field strength at P
switch K during this time interval should be
V: the electric potential at P
W: the energy stored in the capacitor
A.
B.
C.
D.
+15 C, from P to Q
+15 C, from Q to P
+35 C, from P to Q
+35 C, from Q to P
E
V
W
A.
decrease
increase
decrease
B.
decrease
decrease
decrease
C.
remain unchanged
decrease
decrease
D.
remain unchanged
increase
increase
AL-MC-Capacitor / p.9
35.
(04-IIA-25)
Find the ratio of the total electrical energy stored in the
Two circuits, (1) an (2), each connects two
capacitors in circuit (1) to that in circuit (2) when a
identical capacitors with a d.c. supply of e.m.f. E
steady state is reached.
and two resistors as shown.
36.
(05-IIA-16)
A.
2:1
B.
1:2
C.
4:1
D.
1:4