Physics 1029A/B Study Guide - Final Guide: Surface Charge, Point Particle, Relative Permittivity

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orangealligator209

26 Jan 2015

School

Western University

Department

Physics

Course

Physics 1029A/B

Professor

Martin Zinke- Allmang

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Document Summary

When two conducting plates are charged with an equal amount of charge of opposite signs. Three quantities characterize capacitors: surface charge density , capacitance c. Ratio of the charge on each plate to the potential difference across capacitor. Large c = lots of charge = small potential difference: di-electric constant q=c v. Potential difference across a parallel plate capacitor is proportional to the charge on the plates. Capacitance of a parallel plate depends only on geometric properties. Proportional to the area of the plates and inversely proportional to the width of the gab between plates. Dimensionless correction factor dielectric constant. Material constant defined for each material. X 0 = permittivity of dielectric. Q( amount of charge transfered) v (final potential difference) Established when electrons move collectively in a common direction. Requires an electric force acting on electrons. Such force causes acceleration of each electron according to (f = m * a)

Related Questions

A parallel-plate capacitor is connected to a battery of electric potential difference V. If the plate separation is decreased, do the following quantities increase, decrease, or remain the same:

(a) the capacitor’s capacitance,

(b) the potential difference across the capacitor,

(d) the energy stored by the capacitor,

(e) the magnitude of the electric field between the plates,

(f ) the energy density of that electric field?

harlequingnat799

To understand the meaning of capacitance and ways of calculating capacitance.

When a positive charge q is placed on a conductor that is insulated from ground, an electric field emanates from the conductor to ground, and the conductor will have a nonzero potential V relative to ground. If more charge is placed on the conductor, this voltage will increase proportionately. The ratio of charge to voltage is called the capacitance C of this conductor: C=q/V.

Capacitance is one of the central concepts in electrostatics, and specially constructed devices called capacitors are essential elements of electronic circuits. In a capacitor, a second conducting surface is placed near the first (they are often called electrodes), and the relevant voltage is the voltage between these two electrodes.

This tutorial is designed to help you understand capacitance by assisting you in calculating the capacitance of a parallel-plate capacitor, which consists of two plates each of area A separated by a small distanced with air or vacuum in between. In figuring out the capacitance of this configuration of conductors, it is important to keep in mind that the voltage difference is the line integral of the electric field between the plates.

Assume that charge -q is placed on the top plate, and +q is placed on the bottom plate. What is the magnitude of the electric field E between the plates?
What is the voltage V between the plates of the capacitor?

beigemouse1

A parallel plate capacitor is charged to a potential difference of100 V and disconnected from the source. A slab of dielectric isthen inserted between the plates. Which of the followingchanges?
a. the potential difference
b. the capacitance
c. the charge on the plates
d. 1 and 2
e. all of the above
f. none of the above

2. Consider inserting a slab of dielectric material is insertedbetween the plates of a charged capacitor. The electric field inthe dielectric is
a. largest near the positively charged plate.
b. the same everywhere.
c. largest near the negatively charged plate.
d. None of the above.

3.A certain amount of work is required to bring two point charges qnear each other until they are a distance d apart. If the magnitudeof the point charges were doubled to 2q, would the work requiredalso double?
a. yes
b. no
C. It depends on the signs of the charges.
D. None of the above.

Physics 1029A/B Study Guide - Final Guide: Surface Charge, Point Particle, Relative Permittivity

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