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{{Chapter 24Chapter 24

CapacitanceCapacitance

© 2012 Pearson Education, Inc.

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

A. Ceq = 18 F

B. Ceq = 9 F

C. Ceq = 6 F

D. Ceq = 4 F

E. Ceq = 2 F

Q24.3a

b

12 F

6 F

© 2012 Pearson Education, Inc.

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

A. Ceq = 18 F

B. Ceq = 9 F

C. Ceq = 6 F

D. Ceq = 4 F

E. Ceq = 2 F

A24.3a

b

12 F

6 F

© 2012 Pearson Education, Inc.

A 12-F capacitor and a 6-F capacitor are connected together as shown. If the charge on the 12-F capacitor is 24 microcoulombs (24 C), what is the charge on the 6-F capacitor?

A. 48 C

B. 36 C

C. 24 C

D. 12 C

E. 6 C

Q24.4a

b

12 F

6 F

© 2012 Pearson Education, Inc.

A 12-F capacitor and a 6-F capacitor are connected together as shown. If the charge on the 12-F capacitor is 24 microcoulombs (24 C), what is the charge on the 6-F capacitor?

A. 48 C

B. 36 C

C. 24 C

D. 12 C

E. 6 C

A24.4a

b

12 F

6 F

© 2012 Pearson Education, Inc.

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

A. Ceq = 18 F

B. Ceq = 9 F

C. Ceq = 6 F

D. Ceq = 4 F

E. Ceq = 2 F

Q24.5a

b

12 F 6 F

© 2012 Pearson Education, Inc.

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

A. Ceq = 18 F

B. Ceq = 9 F

C. Ceq = 6 F

D. Ceq = 4 F

E. Ceq = 2 F

A24.5a

b

12 F 6 F

© 2012 Pearson Education, Inc.

A. 48 C

B. 36 C

C. 24 C

D. 12 C

E. 6 C

Q24.6a

b

12 F 6 F

A 12-F capacitor and a 6-F capacitor are connected together as shown. If the charge on the 12-F capacitor is 24 microcoulombs (24 C), what is the charge on the 6-F capacitor?

© 2012 Pearson Education, Inc.

A. 48 C

B. 36 C

C. 24 C

D. 12 C

E. 6 C

A24.6a

b

12 F 6 F

A 12-F capacitor and a 6-F capacitor are connected together as shown. If the charge on the 12-F capacitor is 24 microcoulombs (24 C), what is the charge on the 6-F capacitor?

© 2012 Pearson Education, Inc.

Q24.7

A. becomes 4 times greater.

B. becomes twice as great.

C. remains the same.

D. becomes 1/2 as great.

E. becomes 1/4 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, the energy stored in the capacitor

© 2012 Pearson Education, Inc.

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 4 times greater.

B. becomes twice as great.

C. remains the same.

D. becomes 1/2 as great.

E. becomes 1/4 as great.

A24.7

© 2012 Pearson Education, Inc.

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 remains the same.

C. The potential difference decreases.

D. not enough information given to decide

Q24.8

© 2012 Pearson Education, Inc.

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 remains the same.

C. The potential difference decreases.

D. not enough information given to decide

A24.8

© 2012 Pearson Education, Inc.

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 remains the same.

C. The stored energy decreases.

D. not enough information given to decide

Q24.9

© 2012 Pearson Education, Inc.

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 remains the same.

C. The stored energy decreases.

D. not enough information given to decide

A24.9

© 2012 Pearson Education, Inc.

You slide a slab of dielectric between the plates of a parallel-plate capacitor. As you do this, the potential difference between the plates remains constant.

What effect does adding the dielectric have on the amount of charge on each of the capacitor plates?

A. The amount of charge increases.

B. The amount of charge remains the same.

C. The amount of charge decreases.

D. not enough information given to decide

Q24.10

© 2012 Pearson Education, Inc.

You slide a slab of dielectric between the plates of a parallel-plate capacitor. As you do this, the potential difference between the plates remains constant.

What effect does adding the dielectric have on the amount of charge on each of the capacitor plates?

A. The amount of charge increases.

B. The amount of charge remains the same.

C. The amount of charge decreases.

D. not enough information given to decide

A24.10

© 2012 Pearson Education, Inc.

You slide a slab of dielectric between the plates of a parallel-plate capacitor. As you do this, the potential difference between the plates remains constant.

What effect does adding the dielectric have on the energy stored in the capacitor?

A. The stored energy increases.

B. The stored energy remains the same.

C. The stored energy decreases.

D. not enough information given to decide

Q24.11

© 2012 Pearson Education, Inc.

You slide a slab of dielectric between the plates of a parallel-plate capacitor. As you do this, the potential difference between the plates remains constant.

What effect does adding the dielectric have on the energy stored in the capacitor?

A. The stored energy increases.

B. The stored energy remains the same.

C. The stored energy decreases.

D. not enough information given to decide

A24.11

© 2012 Pearson Education, Inc.

Molecular model of induced charge - IMolecular model of induced charge - I

• Figures 24.17 Figures 24.17 (right) and 24.18 (right) and 24.18 (below) show the (below) show the effect of an effect of an applied electric applied electric field on polar and field on polar and nonpolar nonpolar molecules.molecules.

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Molecular model of induced charge - IIMolecular model of induced charge - II• Figure 24.20 below shows Figure 24.20 below shows polarizationpolarization of the dielectric of the dielectric

and how the induced charges reduce the magnitude of the and how the induced charges reduce the magnitude of the resultant electric field.resultant electric field.

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Some dielectric constantsSome dielectric constants

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Dielectric breakdownDielectric breakdown• If the electric field is strong enough, If the electric field is strong enough, dielectric dielectric

breakdownbreakdown occurs and the dielectric becomes a occurs and the dielectric becomes a conductor.conductor.

• The The dielectric strengthdielectric strength is the maximum electric field is the maximum electric field the material can withstand before breakdown occurs.the material can withstand before breakdown occurs.

• Table 24.2 shows the dielectric strength of some Table 24.2 shows the dielectric strength of some insulators.insulators.

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Dielectrics - SummaryDielectrics - Summary

• A A dielectricdielectric is a is a nonconducting material. nonconducting material. Most capacitors have Most capacitors have dielectric between their dielectric between their plates. (See Figure 24.13 at plates. (See Figure 24.13 at upper right.)upper right.)

• The The dielectric constantdielectric constant of the of the material is material is K = C/CK = C/C00 > 1. > 1.

• Dielectric Dielectric increasesincreases the the capacitance and the energy capacitance and the energy density by a factor density by a factor KK..

• Figure 24.15 (lower right) Figure 24.15 (lower right) shows how the dielectric shows how the dielectric affects the electric field affects the electric field between the plates.between the plates.