3 - Capacitors

They are devices for storing charges.

Capacitors

Where are capacitors found? (3)

1. computer motherboards

2. photoflash units

3. television and radio circuits

Simplest capacitor consists of _____ plates separated by thin sheet of insulating material or dielectric.

two parallel conducting

It is the ability of a capacitor to store charges.

Capacitance (C)

It is the SI unit of capacitance.

Farad (F)

Who is Farad named after?

Michael Faraday

1 F is equal to?

1 coulomb per volt

Capacitance of a parallel plate capacitor is affected by? (3)

1. Area of plates

2. Distance between the plates

3. Insulating material or dielectric between them

It is the ability of a material to polarize in response to the field, reducing the total electric field inside the material.

Permittivity

Describe the layers.

Negative - Dieletric - Positive

Capacitors are also widely used in? (3)

1. Electronic circuits - blocking direct current while allowing alternating current to pass

2. Filter networks - smoothing the output of power supplies

3. resonant circuits - that tune radios to particular frequencies and for many other purposes

(Storing a charge between the plates) Electrons on the left plate are attracted toward the positive _____ of the voltage source.

terminal

(Storing a charge between the plates) This leaves an excess of _____.

positively charged holes

(Storing a charge between the plates) The electrons are pushed toward the _____.

right plate

(Storing a charge between the plates) Excess electrons leave a _____.

negative charge

Give types of capacitors and how to determine them. (3)

1. Mica

2. Ceramic

3. Plastic film

(dielectric material determines the type)

What is it called if a capacitor can only be connected one way around?

Polarised

_____ capacitors are polarised.

Electrolytic

They are capacitors used in communication, equipment, radios, televisions and VCRs.

Variable capacitors

How can variable capacitors be adjusted?

tuning controls

They are internal adjusted capacitors that a consumer cannot adjust.

Trimmers

What are the three important rules for capacitors in series?

1. The reciprocal of the total capacitance is equal to the sum of the reciprocals of the individual capacitance. Adding a capacitor in series decreases the total capacitance of the combination.

2. The total potential difference or total voltage is the sum of the potential differences across each capacitor.

3. The total charge is equal to the individual charge stored in each capacitor.

What are the three important rules for capacitors in parallel?

1. The total capacitance is the sum of the individual capacitances.

2. The voltage across all capacitors is equal to the voltage of each capacitor.

3. The total charge is equal to the sum of the individual charges.