capacitance

Question 1

what is meant by capacitance

Answer 1

• charge stored by a capacitor per unit potential difference

C = Q / V

Question 2

what is a capacitor?

Answer 2

• electrical component that stores charge
• made up of two conducting parallel plates with a gap between them thats seperated with a dielectric
• opposite charges build up on the parallel plates when connected to a power source

Question 3

what is permittivity

Answer 3

• ability to store an electric field in the material

Question 4

how do we calculate the dielectric constant

Answer 4

ratio of permittivity of the dielectric to the permittivity of free space

Question 5

how can the capacitance of a capacitor be measured

Answer 5

• measuring the area of the plates
• the distance between the plates
• relative permittivity of the dielectric in the gap of the capacitor

C = Aeoer / d

Question 6

how does a dielectric work

Answer 6

• formed of polar molecules
• when there is no e field, molecules are arranged randomly
• ## when an e field is present, the molecules align themselves with the field

Question 7

what are the three equations for energy stored by a capacitor

Answer 7

E = 1/2QV

E = 1/2 CV^2

E = 1/2 Q^2 / C

Question 8

what happens to the pd across the resistor and potential difference across the capacitor after the switch is closed

Answer 8

• pd is formed across the capacitor
• pd across resistor decreases
• pd across capacitor increase to max emf exponentially
• pd across resistor decreases to 0 exponentially