Physics 12 METU D. F. HIGH SCHOOL Capacitors … - Capacitor (concept Test... · Physics 12 Capacitors Worksheet : Capacitors (Concept Test) 1. 2. 1 METU D. F. HIGH SCHOOL 2015-2016

Physics 12 Capacitors Worksheet : Capacitors (Concept Test)

1. 2.

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METU D. F. HIGH SCHOOL 2015-2016 ACADEMIC YEAR

GRADE 12 / PHYSICS CAPACITORS (Multiple Choice Questions)

1. A parallel plate capacitor is charged and dismantled from the battery. If a material of dielectric constant K=3 is inserted between the plates, which one of the following can be observed? A) Voltage on the capacitor is multiplied by 3. B) Voltage on the capacitor is divided by 3. C) Charge on the plates is multiplied by 3. D) Charge on the plates is divided by 3. E) Voltage on the capacitor will not change. 2. In the circuit, the energy stored in 5

€

µF capacitor is E1. After the switch S1 is opened and S2 is closed the energy stored in the same capacitor becomes E2.

What is the ratio of E1/E2? A) 10 B) 15 C) 20 D) 25 E) 50 3. Two capacitors have capacitances C1 and C2 such that C1>C2. I. If they are connected in series, C1 stores more energy

than C2. II. If they are connected in parallel, C1 stores more

charge than C2. III. If they are connected in series, C1 has smaller voltage

than C2. Which of the above statement(s) is/are correct? A) I only B) III only C) I and II D) II and III E) I, II and III

Questions 4 through 6 pertain to the following situation: The figure below shows four parallel plate capacitors: A, B, C and D. Each capacitor carries the same charge q and has the same plate area A. As suggested by the figure, the plates of capacitors A and C are separated by a distance d while those of B and D are separated by a distance 2d. Capacitors A and B are maintained in vacuum while capacitors C and D contain dielectrics with constant K=5.

4. Which list below places the capacitors in order of increasing capacitance? A) A, B, C, D B) B, A, C, D C) A, B, D, C D) B, A, D, C E) D, C, B, A 5. Which capacitor has the largest potential difference between its plates? A) A B) B C) C D) D 6. Which capacitor is storing the greatest amount of electric potential energy? A) A B) B C) C D) D 7. The charge of a parallel plate capacitor is doubled by increasing the voltage. Which one of the following statements is true concerning the capacitance of this parallel plate capacitor? A) The capacitance is decreased to one half of its original

value. B) The capacitance is increased to twice its original

value. C) The capacitance remains unchanged. D) The capacitance depends on the electric field between

the plates. E) The capacitance depends on the potential difference

across the plates.

20µF

S1

S2

5µF

10V

+ -

d d 2d 2d

A B C D

vacuum Dielectric (K= 5)

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across the plates.

20µF

S1

S2

5µF

10V

+ -

d d 2d 2d

A B C D


Capacitance of the capacitor is multiplied by 3. It is dismantled from the battery. This means its

charge is the same. So, the voltage across the plates of the

capacitor is divided by 3. Capacitance and voltage are

inversely proportional when the charge is kept constant.

Energy stored in a capacitor is directly proportional to the square of the amount

of charge it stores.

S1 closed & S2 open Q1=5Q

S1 open & S2 closed Q2=Q

E1/E2=25

Physics 12 Worksheet : Capacitors (Concept Test)

3.

Capacitors

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across the plates.

20µF

S1

S2

5µF

10V

+ -

d d 2d 2d

A B C D


1




€











across the plates.

20µF

S1

S2

5µF

10V

+ -

d d 2d 2d

A B C D


I. When they are connected in series, the charges stored in both capacitors are the same.

II. When they are connected in parallel, the one having greater capacitance stores more charge.

III. When they are connected in series, the one having greater capacitance has fewer voltage.

Voltage and capacitance are inversely proportional for series capacitors.

Charge is the same. The one having fewer capacitance has more voltage

between its plates.

CA=ε.A/d CB=ε.A/2d

CC=5ε.A/d CD=5ε.A/2d

Charge is the same. The one having fewer capacitance stores more energy.


7. 8.

Capacitors

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across the plates.

20µF

S1

S2

5µF

10V

+ -

d d 2d 2d

A B C D


2

8. The capacitance of the capacitor in Figure-1 is “C”. An insulator having dielectric constant K=2 is inserted between the plates as shown in Figure-2.

What is the capacitance of the capacitor in the Figure-2? A) C/3 B) 2C/3 C) 4C/3 D) 3C/2 E) 5C/2 9. The capacitors 3C and X have the same amount of charge.

What is the capacitance of X? A) 2C B) 3C C) 4C D) 6C E) 9C 10. The wires K and L do not touch to each other. The capacitances of the capacitors are 6C, 3C and 2C.

I. The capacitor 3C is short-circuited. II. The capacitors 6C and 3C are in series combination. III. The charge of 6C is three times the charge of 2C. Which of the above statement(s) is/are correct? A) Only I B) Only II C) Only III D) I and III E) II and III

11. Two capacitors are first charged (Figure-I) and they are connected across a resistor as shown (Figure-II).

If the total electric energy stored in Figure-I is 9 J, then what is the heat energy dissipated by the resistor until steady state is reached? A) 8 B) 5 C) 4 D) 2 E) 1 12. The circuit is assembled with identical capacitors. The capacitor that has the minimum energy acquires 4 J potential energy.

What is the potential energy of the capacitor that acquires the maximum energy? A) 8 B) 16 C) 18 D) 32 E) 36 13. Capacitors K and L are charged as in figure-1. These capacitors are reconnected as shown in figure-2.

What is the potential difference between points X and Y? A) V/9 B) V/8 C) 3V/4 D) 2V/3 E) V/2 14. Which of the below sentences is correct? A) The capacitor connected to a battery act as a

conducting wire. B) The capacitor has a constant resistance in DC circuit. C) The capacitor has zero resistance at the instant it is

connected across a battery. D) After a capacitor is connected to a battery its

resistance slowly decreases. E) The current passing through a fully charged capacitor

is maximum.

When the voltage across the plates of a capacitor is doubled, the amount of charge

stored on the capacitor is doubled. Its capacitance remains unchanged. Its

capacitance depends on some physical factors not the voltage.

For Figure-1;

C=ε.A/2d

For Figure-2;

The part with air (C1) and the

part with dielectric (C2) are like

two series capacitor.

C1=ε.A/(d/2)=2C

C2=2ε.A/(d/2)=4C

Cnew=(2C.4C)/(2C+4C)=4C/3

For Figure-1;

C=ε.A/2d

For Figure-2;

The part with air (C1) and the

part with dielectric (C2) are like

two series capacitor.

C1=ε.A/(d/2)=2C

C2=2ε.A/(d/2)=4C

Cnew=(2C.4C)/(2C+4C)=4C/3


9. 10.

Capacitors

2












is maximum.

2












is maximum.

3Q

3Q

Let’s say that the charge on X

is 3Q

The charge stored on C is Q and the total charge on the main branch is 4Q

The total charge stored on 2C and X is 4Q. so the charge of 2C capacitor is Q.

Q/2C=3Q/X

X=6C

2C and X are parallel and their voltages are equal.

A

A

B

B

All the capacitors are parallel because all of them are connected between A and B. So, statements I and II are

wrong.

They ar e all parallel. Then the amount of charges that they store is directly proportional to their capacitances. So, 6C stores three times the charge of 2C. Only this

statement is correct.


11. 12.

Capacitors

2












is maximum.

2












is maximum.

For Figure-1; QC=CV and Q2C=2CV

Etotal=(3C.V2)/2=9 J then CV2=6 J

For Figure-2; Qtotal=2CV-CV=CV

For capacitor C; Q=CV/3 then Vfinal=V/3

Etotal=(3C.(V2/9)/2=1 J then

Eheat=9-1=8 J

Emin=CV2/2=4 J

Emax=C.9V2/2=9CV2/2

Emax=9.4=36 J


13. 14.

Capacitors

2







What is the potential energy of the capacitor that acquires the maximum energy? A) 8 B) 16 C) 18 D) 32 E) 36 13. Capacitors K and L are charged as in Figure-1. These capacitors are reconnected as shown in Figure-2.





is maximum.

2







What is the potential energy of the capacitor that acquires the maximum energy? A) 8 B) 16 C) 18 D) 32 E) 36 13. Capacitors K and L are charged as in Figure-1. These capacitors are reconnected as shown in Figure-2.





is maximum.

QK=4CV

QL=2CV

Figure-1 Figure-2

Qtotal=4CV-2CV=2CV

QK-final=2CV/3

VXY=(2CV/3)/C

VXY=V/3

A capacitor has zero resistance when it is connected to the terminals of a

battery, after fully charged it behaves like an open circuit, no current will be observed. Its resistance is thought as

infinite.

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Physics 12 METU D. F. HIGH SCHOOL Capacitors … - Capacitor (concept Test... · Physics 12 Capacitors Worksheet : Capacitors (Concept Test) 1. 2. 1 METU D. F. HIGH SCHOOL 2015-2016