Question 1

If the plate area of an isolated charged parallel-plate capacitor is doubled:

Accepted Answer

A)  the electric field is doubled 
B)  the potential difference is halved 
C)  the charge on each plate is halved 
D)  the surface charge density on each plate is doubled 
E)  none of the above

Question 2

An air-filled parallel-plate capacitor has a capacitance of 1 pF. The plate separation is then doubled and a wax dielectric is inserted, completely filling the space between the plates. As a result, the capacitance becomes 2 pF. The dielectric constant of the wax is:

Accepted Answer

A)  0.25 
B)  0.50 
C)  2.0 
D)  4.0 
E)  8.0

Question 3

A parallel-plate capacitor has a plate area of 0.2 m2 and a plate separation of 0.1 mm. If the charge on each plate has a magnitude of 4 *10-6 C the potential difference across the plates is approximately:

Accepted Answer

A)  0 V 
B)  4 * 10-2 V 
C)  2 *102 V 
D)  2 *105 V 
E)  4 * 108 V

Question 4

Each of the three 25-$\mu$F capacitors shown is initially uncharged. How many coulombs of charge pass through the ammeter A after the switch S is closed?

Accepted Answer

A)  0.033 C 
B)  0.10 C 
C)  0.30 C 
D)  10 C 
E)  none of these

Question 5

The quantity (1/2)$\varepsilon$0E2 has the dimensions of:

Accepted Answer

A)  energy/farad 
B)  energy/coulomb 
C)  energy 
D)  energy/volume 
E)  energy/volt

Question 6

Capacitors C1 and C2 are connected in parallel and a potential difference is applied to the combination. If the capacitor that is equivalent to the combination has the same potential difference, then the charge on the equivalent capacitor is the same as:

Accepted Answer

A)  the charge on C1 
B)  the sum of the charges on C1 and C2 
C)  the difference of the charges on C1 and C2 
D)  the product of the charges on C1 and C2 
E)  none of the above

Question 7

The capacitance of a single isolated spherical conductor with radius R is proportional to:

Accepted Answer

A)  R 
B)  R2 
C)  1/R 
D)  1/R2 
E)  none of these

Question 8

The capacitance of a parallel-plate capacitor can be increased by:

Accepted Answer

A)  increasing the charge 
B)  decreasing the charge 
C)  increasing the plate separation 
D)  decreasing the plate separation 
E)  decreasing the plate area

Question 9

Let Q denote charge, V denote potential difference and U denote stored energy. Of these quantities, capacitors in series must have the same:

Accepted Answer

A)  Q only 
B)  V only 
C)  U only 
D)  Q and U only 
E)  V and U only

Question 10

A parallel-plate capacitor, with air dielectric, is charged by a battery, after which the battery is disconnected. A slab of glass dielectric is then slowly inserted between the plates. As it is being inserted:

Accepted Answer

A)  a force repels the glass out of the capacitor 
B)  a force attracts the glass into the capacitor 
C)  no force acts on the glass 
D)  a net charge appears on the glass 
E)  the glass makes the plates repel each other

Question 11

To charge a 1-F capacitor with 2 C requires a potential difference of:

Accepted Answer

A)  0.2 V 
B)  0.5 V 
C)  2 V 
D)  5 V 
E)  none of these

Question 12

The capacitance of a cylindrical capacitor can be increased by:

Accepted Answer

A)  decreasing both the radius of the inner cylinder and the length 
B)  increasing both the radius of the inner cylinder and the length 
C)  increasing the radius of the outer cylindrical shell and decreasing the length 
D)  decreasing the radius of the inner cylinder and increasing the radius of the outer cylindrical shell 
E)  only by decreasing the length

Question 13

Capacitors A and B are identical. Capacitor A is charged so it stores 4 J of energy and capacitor B is uncharged. The capacitors are then connected in parallel. The total stored energy in the capacitors is now:

Accepted Answer

A)  16 J 
B)  8 J 
C)  4 J 
D)  2 J 
E)  1 J

Question 14

What happens to the atoms in a dielectric when it is placed between the plates of a charged capacitor?

Accepted Answer

A)  They begin to conduct electricity. 
B)  They create an induced electric field that is in the opposite direction of the field due to the charges on the plates. 
C)  They create an induced electric field that is in the same direction as the field due to the charges on the plates. 
D)  They completely cancel the electric field due to the charges on the plates. 
E)  They rotate so their positive ends are towards the positively charged plate.

Question 15

Two parallel-plate capacitors with the same plate area but different capacitance are connected in parallel to a battery. Both capacitors are filled with air. The quantity that is the same for both capacitors when they are fully charged is:

Accepted Answer

A)  potential difference 
B)  energy density 
C)  electric field between the plates 
D)  charge on the positive plate 
E)  plate separation

Question 16

An air-filled capacitor is charged, and then a dielectric is inserted. As a result, there is an induced charge on the dielectric. What is the difference between induced charge and free charge?

Accepted Answer

A)  There is no difference. 
B)  Induced charge does not result in a net charge on the dielectric. 
C)  Induced charge is smaller than free charge. 
D)  Free charge creates an electric field, but induced charge does not. 
E)  Free charge creates an electric potential, but induced charge does not.

Question 17

A battery is used to charge a series combination of two identical capacitors. If the potential difference across the battery terminals is V and total charge Q flows through the battery during the charging process then the charge on the positive plate of each capacitor and the potential difference across each capacitor are:

Accepted Answer

A)  Q/2 and V/2, respectively 
B)  Q and V, respectively 
C)  Q/2 and V, respectively 
D)  Q and V/2, respectively 
E)  Q and 2V, respectively

Question 18

A 20-µF capacitor is charged to 200 V. Its stored energy is:

Accepted Answer

A)  4000 J 
B)  4 J 
C)  0.4 J 
D)  0.1 J 
E)  0.004 J

Question 19

If the plate separation of an isolated charged parallel-plate capacitor is doubled:

Accepted Answer

A)  the electric field is doubled 
B)  the potential difference is halved 
C)  the charge on each plate is halved 
D)  the surface charge density on each plate is doubled 
E)  none of the above

Question 20

Let Q denote charge, V denote potential difference and U denote stored energy. Of these quantities, capacitors in parallel must have the same:

Accepted Answer

A)  Q only 
B)  V only 
C)  U only 
D)  Q and U only 
E)  V and U only

Exam 25: Capacitance

If the plate area of an isolated charged parallel-plate capacitor is doubled:

An air-filled parallel-plate capacitor has a capacitance of 1 pF. The plate separation is then doubled and a wax dielectric is inserted, completely filling the space between the plates. As a result, the capacitance becomes 2 pF. The dielectric constant of the wax is:

A parallel-plate capacitor has a plate area of 0.2 m² and a plate separation of 0.1 mm. If the charge on each plate has a magnitude of 4 *10^-6 C the potential difference across the plates is approximately:

The quantity (1/2) $\varepsilon$ ₀E² has the dimensions of:

Capacitors C₁ and C₂ are connected in parallel and a potential difference is applied to the combination. If the capacitor that is equivalent to the combination has the same potential difference, then the charge on the equivalent capacitor is the same as:

The capacitance of a single isolated spherical conductor with radius R is proportional to:

The capacitance of a parallel-plate capacitor can be increased by:

Let Q denote charge, V denote potential difference and U denote stored energy. Of these quantities, capacitors in series must have the same:

A parallel-plate capacitor, with air dielectric, is charged by a battery, after which the battery is disconnected. A slab of glass dielectric is then slowly inserted between the plates. As it is being inserted:

To charge a 1-F capacitor with 2 C requires a potential difference of:

The capacitance of a cylindrical capacitor can be increased by:

Capacitors A and B are identical. Capacitor A is charged so it stores 4 J of energy and capacitor B is uncharged. The capacitors are then connected in parallel. The total stored energy in the capacitors is now:

What happens to the atoms in a dielectric when it is placed between the plates of a charged capacitor?

Two parallel-plate capacitors with the same plate area but different capacitance are connected in parallel to a battery. Both capacitors are filled with air. The quantity that is the same for both capacitors when they are fully charged is:

An air-filled capacitor is charged, and then a dielectric is inserted. As a result, there is an induced charge on the dielectric. What is the difference between induced charge and free charge?

A 20-µF capacitor is charged to 200 V. Its stored energy is:

If the plate separation of an isolated charged parallel-plate capacitor is doubled:

Let Q denote charge, V denote potential difference and U denote stored energy. Of these quantities, capacitors in parallel must have the same:

Exam 25: Capacitance

If the plate area of an isolated charged parallel-plate capacitor is doubled:

An air-filled parallel-plate capacitor has a capacitance of 1 pF. The plate separation is then doubled and a wax dielectric is inserted, completely filling the space between the plates. As a result, the capacitance becomes 2 pF. The dielectric constant of the wax is:

A parallel-plate capacitor has a plate area of 0.2 m2 and a plate separation of 0.1 mm. If the charge on each plate has a magnitude of 4 *10-6 C the potential difference across the plates is approximately:

Each of the three 25- μ\muμ F capacitors shown is initially uncharged. How many coulombs of charge pass through the ammeter A after the switch S is closed?

The quantity (1/2) ε\varepsilonε 0E2 has the dimensions of:

Capacitors C1 and C2 are connected in parallel and a potential difference is applied to the combination. If the capacitor that is equivalent to the combination has the same potential difference, then the charge on the equivalent capacitor is the same as:

The capacitance of a single isolated spherical conductor with radius R is proportional to:

The capacitance of a parallel-plate capacitor can be increased by:

Let Q denote charge, V denote potential difference and U denote stored energy. Of these quantities, capacitors in series must have the same:

A parallel-plate capacitor, with air dielectric, is charged by a battery, after which the battery is disconnected. A slab of glass dielectric is then slowly inserted between the plates. As it is being inserted:

To charge a 1-F capacitor with 2 C requires a potential difference of:

The capacitance of a cylindrical capacitor can be increased by:

Capacitors A and B are identical. Capacitor A is charged so it stores 4 J of energy and capacitor B is uncharged. The capacitors are then connected in parallel. The total stored energy in the capacitors is now:

What happens to the atoms in a dielectric when it is placed between the plates of a charged capacitor?

Two parallel-plate capacitors with the same plate area but different capacitance are connected in parallel to a battery. Both capacitors are filled with air. The quantity that is the same for both capacitors when they are fully charged is:

An air-filled capacitor is charged, and then a dielectric is inserted. As a result, there is an induced charge on the dielectric. What is the difference between induced charge and free charge?

A 20-µF capacitor is charged to 200 V. Its stored energy is:

If the plate separation of an isolated charged parallel-plate capacitor is doubled:

Let Q denote charge, V denote potential difference and U denote stored energy. Of these quantities, capacitors in parallel must have the same:

A parallel-plate capacitor has a plate area of 0.2 m² and a plate separation of 0.1 mm. If the charge on each plate has a magnitude of 4 *10^-6 C the potential difference across the plates is approximately:

The quantity (1/2) $\varepsilon$ ₀E² has the dimensions of:

Capacitors C₁ and C₂ are connected in parallel and a potential difference is applied to the combination. If the capacitor that is equivalent to the combination has the same potential difference, then the charge on the equivalent capacitor is the same as: