Capacitance and Capacitors

Question 1

Capacitor

Answer 1

-Device in electrical circuits that can store charge + electrical energy

Question 2

Capacitance formula

Answer 2

C = Q/V

Question 3

unit of capacitance

Answer 3

-Coulomb/Volts, called the Farad (F)

Question 4

Charged capacitor

Answer 4

• Neutral overall
• Stores equal amounts of pos + neg charge
• maintains charge separation

Question 5

What is capacitance of a capacitor?

Answer 5

-The charge storing capacity of a capacitor

Question 6

Electric field in capactiros

Answer 6

• exists inside a charge capacitor

- between pos + neg charge separation

Question 7

Simplest type of capacitor

Answer 7

• parallel plate capacitor

- consists of two parallel metal plates each of area A, separated by distance d

Question 8

current by definition

Answer 8

in opposite direction to flow of electrons

Question 9

voltage drop across capacitor

Answer 9

when its the same as that of the battery, V, charging ceases

Question 10

dielectrics

Answer 10

-an electrical insulator that can be polarized by an applied electric field

Question 11

examples of dielectrics

Answer 11

• stressed plastic
• piezo-electric crystal

-will produce a spark

Question 12

dielectric in a uniform electric field

Answer 12

• a dipole moment is induced on the molecules throughout the volume
• produces a volume polarization

Question 13

Putting dielectric material in between plates of a capacitor

Answer 13

-surface charge densities due to dipoles act to reduce electric field in capacitor

Question 14

dielectric constant

Answer 14

εᵣ ,

amount that field is reduced

Question 15

New E field formula

Answer 15

E = E₀/εᵣ

Question 16

Total potential energy increase

Answer 16

U = Q²/2C

also
U = (1/2)(QV) = (1/2)(CV²)