capacitors and filters

How is a capacitor constructed?

Two conductive plates separated by an insulating dielectric

How does capacitance depend on the physical properties of a capacitor. 

Plate area, plate spacing, and dielectric material

What is the definition of capacitance?  

Ability to store electric charge per volt

What are the units of capacitance?

• Farads

How do we represent the quantity of capacitance in an equation?

C

What is capacitive reactance? 

Opposition a capacitor gives to AC

What are the units of reactance?

• Ohms

How do we represent reactance in an equation? 

x_c

Why does frequency affect capacitive reactance? 

Higher frequency allows faster charge/discharge, reducing opposition

For a known capacitance, how is reactance computed for a given frequency?

x_c = 1/2pifc

How does a capacitor behave at very, very low frequencies? 

Acts like an open circuit

How does a capacitor behave at very, very high frequencies? 

Acts like a short circuit

What is meant by the “cutoff frequency” of an RC low-pass filter? 

Frequency where output drops to 70.7% (−3 dB)

How is the cutoff frequency calculated from the R and C values? 

f_c = 1/2piRC