Capacitance

Question 1

what is a capacitor?

Answer 1

an electrical component that stores charge

Question 2

what is the equation for capacitance?

Answer 2

C=Q/V

Question 3

What is Capacitance?

Answer 3

the charge stored by a capacitor per unit potential difference

Question 4

what is permittivity?

Answer 4

the measure of the ability to store an electric field in a material

Question 5

What is the the dielectric?

Answer 5

relative permittivity

Question 6

what is the equation for the dielectric constant (relative permittivity)?

Answer 6

εᵣ=ε/ε₀

Question 7

what is the equation for capacitance with relative permittivity?

Answer 7

C= Aε₀ εᵣ/d

Question 8

what is the dielectric formed of?

Answer 8

polar molecules, which is positive at one end and negative at the other

Question 9

How do polar molecules work?

Answer 9

• when there is no electric field, they move in random directions
• when there is an electric field, they will align themselves with the field, the negative ends will be rotated towards the positive plate of the capacitor and the positive ends to the negative plate. each particle has its own electric field

Question 10

what does the strength of the electric field of polar molecules depend on?

Answer 10

the dielectric’s permittivity, which would oppose the field formed by a capacitor

Question 11

what is the equation for energy stored by a capacitor?

Answer 11

E= 1/2 x QV
or E=1/2 x CV²

Question 12

Explain how a capacitor charges?

Answer 12

once the capacitor is connected to the power supply, current starts to flow and negative charge builds up on the plate of the negative terminal. On the opposite plate, electrons are repelled by the negative charge, therefore these electrons move to the positive terminal and an equal and opposite charge is formed on each plate, creating a potential difference. As the charge across, the potential difference increase, electron flow decreases due to electrostatic repulsion, and current reaches 0.

Question 13

what is the equation for current charging and discharging?

Answer 13

• Charging : I=I₀e^(-t/RC)
• Discharging : I=I₀e^(-t/RC)

Question 14

what is the equation for charge charging and discharging?

Answer 14

• Charging : Q=Q ₀(1-e^(-t/RC))
• Discharging : Q=Q ₀e^(-t/RC)

Question 15

what is the equation for potential difference charging and discharging?

Answer 15

• Charging : V=V₀(1-e^(-t/RC))
• Discharging : V=V₀e^(-t/RC)

Question 16

how do you calculate the time constant from the graphs?

Answer 16

by finding the time where the values are either 0.37 of the initial discharging or 0.63 of the maximum value if charging