Capacitance / Capacitive Reactance

What are capacitors used for?

timers, rectifier smoothing and filtering, power factor correction, motor starting

What is capacitance (C)?

capacitor’s ability to store electric charge in an electrostatic field, opposing changes in voltages across it

What is a farad?

one farad can store charge of one coulomb per volt

What factors affect capacitance?

1. distance between plates

2. area of plates

3. dielectric

How can we check if a capacitor can be used for AC?

peak voltage must not exceed WVDC rating

Charge formula?

Q = I x T

Time constants for capacitors

each time constant is 63.2% of remaining voltage

T (TAU) = R x C

What happens to capacitive reactance when capacitance or frequency changes?

higher capacitance means lower ohmic value.

higher frequency means lower ohmic value.

Where do capacitors store energy?

In an electrostatic field inside the dielectric.