Capacitance

The two conductors a and b are insulated from each other, forming a capacitor. You increase the charge on a to +2Q and increase the charge on b to –2Q, while keeping the conductors in the same positions. As a result of this change, the capacitance C of the two conductors

• A. becomes four times as great. 

• B. becomes twice as great.

• C. remains the same. 

• D. becomes half as great.

• E. becomes one-quarter as great.

You reposition the two plates of a capacitor so that the capacitance doubles. There is vacuum between the plates. If the charges +Q and –Q on the two plates are kept constant in this process, what happens to the potential difference V_ab between the two plates?

• A. V_ab becomes four times as great.

• B. V_ab becomes twice as great.

• C. V_ab remains the same.

• D. V_ab becomes half as great.

• E. V_ab becomes one-quarter as great.

A 12-microfarad and a 6-microfarad capacitor are connected together as shown. What is the equivalent capacitance of the two capacitors in microfarads as a unit?

• 18

• 9

• 6

• 4

• 2

A 12-microfarad and a 6-microfarad capacitor are connected together as shown. If the charge on the 12-microfarad capacitor is 24 microcoulombs, what is the charge on the other capacitor in microcoulombs?

• 48

• 36

• 24

• 12

• 6

A 12-microfarad and a 6-microfarad capacitor are connected together as shown. What is the equivalent capacitance of the two capacitors in microfarads as a unit?

• 18

• 9

• 6

• 4

• 2

A 12-microfarad and a 6-microfarad capacitor are connected together as shown. If the charge on the 12-microfarad capacitor is 24 microcoulombs, what is the charge on the other capacitor in microcoulombs?

• 48

• 36

• 24

• 12

• 6

You reposition the two plates of a capacitor so that the capacitance doubles. There is vacuum between the plates. If the charges +Q and –Q on the two plates are kept constant in this process, the energy stored in the capacitor

• A. becomes four times as great.

• B. becomes twice as great.

• C. remains the same.

• D. becomes half as great.

• E. becomes one-quarter as great.

You want to connect a 12-microfarad capacitor and a 6-microfarad capacitor. How should you connect them so that when the capacitors are charged, the 12-microfarad capacitor will have a greater amount of stored energy than the 6-microfarad capacitor?

• The two capacitors should be in series.

• The two capacitors should be in parallel.

• The two capacitors can be either in series or in parallel—in either case, the 12-microfarad capacitor will have a greater amount of stored energy. 

• The connection should be neither series nor parallel.

• This is impossible no matter how the two capacitors are connected.

You slide a slab of dielectric between the plates of a parallel-plate capacitor. As you do this, the charges on the plates remain constant. What effect does adding the dielectric have on the potential difference between the capacitor plates?

• A. The potential difference increases.

• B. The potential difference decreases.

• C. The potential difference remains the same.

• All of these are possible

You slide a slab of dielectric between the plates of a parallel-plate capacitor. As you do this, the charges on the plates remain constant. What effect does adding the dielectric have on the energy stored in the capacitor?

• A. The stored energy increases.

• B. The stored energy decreases.

• C. The stored energy remains the same.

• All of these are possible