Week 7: Capacitance

What are capacitors?

Capacitors are devices that store electrical charge.

What is the formula for capacitance?

C = Q/Vc

• Q is the charge

• Vc is the voltage along the capacitor

What is the units of capacitance

Faradays or Coulomb per voltage

How does a capacitor work?

a capacitor has two metal plates of distance d away from each other and contain opposite charges. The capacitors are linked by a completed circuit. The opposite charges creates an electrical field

What is charge?

—- (closed circuit linked to a capacitor)

What is discharge?

—\- (open circuit linked to a capacitor)

What is the mathematical relationship between charge and capacitance?

Q = C * Vc

• Q is charge

• C is capacitance

• Vc is voltage across capacitor

What is Guass’s Law

A law that explores the relationship between electrical field and charge density of a given surface; the surface flux is directly proportional to the charge inside an object over the dielectric constant (vacuum or no vacuum)

What is the property of Gauss’s law?

The electric field is normal to the area (surface flux) of a given object

What is Gauss’s Law of Electricity?

upside-down triangle/v or the partial dervitave of the electric field = charge density / the dielectric constant

What is the applicaiton of Gauss’s Law to capacitance?

C = Q/Vc = Enot * A/d

• C is capactiance

• Q is charge

• Vc is voltage of capacitance

• Enot is dielectric constant

• A is area

• d is distance between plates

What is dielectric?

An insulator that produces an induced electric field when applied to capacitors and established an ability for an electric field to be polarized.

What is the dielectric equation (polarized)

Epol = -Xe * Etot

• -Xe is electric susceptability

• Etot is electric field total

What is the dielectric equation (applied)

Eapp = (1 + Xe)Etot = KEtot

• Xe is electric susceptibility

• Etot is electric field total

• K is the dielectric constant for a surface, (1 + Xe), or kappa

What is electric susceptibility (Xe)

The ease in which a electric polarizes; Xe is dimensionless, positive, and sclar

What is the relationship with dielectrics and capacitance?

C = Enot*A*(1+Xe)/d = Enot*A*k/d

• Enot is dielectric constant

• A is area

• K or (1+Xe) is dielectric constant

• d is distance between plates

What is the relationship between dielectric and charge?

Q = Enot * k * A/d

• Enot is the dielectric constnat

• K is the dielectric for a given surface

• A i s area

• d is distance between plates

What is electric line charge?

The application of gauss’s law; used procedural wise to find the capacitance, electric field, or charge of a given object where its electrons flow freely?

What mathematical relationship expressed electric line charge?

RowL = QL/L

• RowL is density of electors on a given linear relationship (linear line charge)

• QL is charge

• L is a given line or slope

EL = RowL/2*pi*Enot*r

• Enot is the dielectric constant

• r is the distance of symmetric line or linear relationship to the the point of interest