Unit 11- Electric Circuits

Capacitor

Storage devices for charge.

When storing charge, they also store electrical potential energy

Parallel-Plate Capacitors

Two parallel conductive sheets separated by some distance

These are the most common types of capacitors

Capacitance

The capacitance of a capacitor measures the capacity for holding charge at a given voltage.

The greater the capacitance, the more charge can be stored

Farad

One coulomb per volt is renamed one farad (abbreviated F): 1 C/V = 1F

Dielectric

One method of keeping the plates of a capacitor apart, which is necessary to maintain charge separation and store potential energy, is to insert an insulating material (a dielectric) between the plates.

An insulating material placed between capacitor plates to increase capacitance.

Dielectric Constant

The dielectric constant, κ, is a property of insulators that determines how much they affect the capacitance.

The κ of vacuum is 1, and all other insulators have a value greater than 1.

Current

The overall amount of charge that moves per unit time.

Drift Velocity

The overall motion of particles (e.g. electrons)

It can be found by averaging all the velocity vectors of each particle.

Voltage

Refers to the change in electric potential across a circuit element or between two points. It is measured in units of volts.

Can be referred to as the potential difference, voltage drop, voltage, or EMF

Direct Current

Occurs when the electricity is always flowing in the same direction in a circuit.

Resistance

The impedance to the flow of electricity through an entire object.

Resistivity

Denoted by ρ

A property of a material that describes the general impedance to the flow of electricity through that type of material

Can be thought of as the density of the nuclei the electrons may strike

Ohms

Measures resistance

Denoted by Ω, omega

Ohm-meters

Measures resistivity

(Ωm)

Ampere

One coulomb per second

Abbreviated A

Kirchoff’s Loop Rule

States that the voltage drop across any complete loop in a circuit is 0 V.

Kirchoff’s Junction Rule

States that the sum of all current flowing into any junction is equal to the current flowing out of the junction.