Physics Chpt. 26 (Electrical Devices) Review

capacitance

Measure of a capacitor's ability to store charge, calculated by the ratio of the magnitude of charge on one plate to the voltage across the two plates, expressed in SI units, farads.

An oscillating dipole consists of an oscillating current that moves back and forth to a straight wire (or other conductor) joining two spheres (or other elements) capable of storing charge.

Describe an oscillatting dipole.

In a parallel arrangement, the two plates of each capacitor are connected directly to the source of current. In a series arrangement, only the negative plate of the first capacitor and the positive plate of the last capacitor are joined directly to the source of current; within the series, the positive plate of the first capacitor is connected to the negative plate of the second, and so on down the line.

Distinguish between a series arrangement and a parallel arrangement capacitors.

The dielectric constant of a material indicates the factor by which capacitance is multiplied when the given material is used as a dielectric. The dielectric strength of a material is the maximum potential gradient that material can withstand before it begins to conduct current.

Distinguish between the dielectric constant and the dielectric strength.

C=E A/d; Where C is the capacitance, E is the permittivity of the dielectric, A busy area of each plate, and d is the distance between the plates.

Given a particular dielectric, by what formula may capacitance be readily computed? Identify each quantity.

An alternating current is regarded as equal in strength to the Direct current that, in the same resistance, would produce heat at the same average rate.

How is the effective value of alternating current defined?

The capacitance of a series arrangement is found by using the equation 1/C = 1/C1 + 1/C2... the capacitance of a parallel arrangement is found by using the equation C = C1 + C2...

How is total capacitance computed for capacitors in series? In parallel?

A kW x hr= 3.6 x 10(6) J

How many joules are in a kilowatt hour?

A joule is a watt per second

How may a joule be restated in terms of power and time units?

Transverse electromagnetic waves are not propagated straight outward from either end of the dipole.

In what directions are TEM waves not propagated from an oscillating dipole?

Oscillating fields are propagated through space in the form of transverse electromagnetic waves

In what form are oscillating fields propagated through space?

inductance

The property in an electrical circuit where a change in the current flowing through that circuit induces an electromotive force (EMF) that opposes the change in current

The current and voltage furnished by the power company must be perfectly in phase.

Under what condition is alternating current correctly described by Ohm's law in the form V(t) = I(t)R.

One coulomb per volt

What are the units of one farad?

P = I(2)R, P = V(2)/R, P=VI

What are three alternative formulas for computing the power expended in a resistance?

If a changing current in one coil induces current in an adjacent coil, the former is called the primary coil and the latter is called the secondary coil.

What is the difference between a primary coil and a secondary coil?

root-mean-square value/RMS value

the effective value of an alternating current

dielectric constant

the factor by which capacitance is multiplied when a certain material is used as the dielectric

joule heat

the heat generated by current when it passes through a resistance, whether a pure resistance or a load resistance.

dielectric strength

the maximum potential gradient that material can withstand before it begins to conduct current

self inductance

the tendency of a loop or a coil to oppose any change in current

Farad

the unit of capacitance; equal to a coulomb per volt

TEM ways

transverse electromagnetic waves

oscillating dipole

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Capacitor/Condenser

A charge storing device consisting of two conductors in near relation but not touching

Hal's current/wall current

AC current with the frequency of 60 Hz; the current furnished by a electric power companies

Positive

As a self-induced EMF of the coil positive or negative when current is decreasing?

Electric and magnetic fields are propagated outward at the speed of light

At what speed are electric and magnetic fields propagated outward?

By increasing the area of each plate, by bringing the plates closer together, or by filling the gap between the plates with a dielectric.

In what three ways may capacitance be increased?

The Henry; H = V x s/A = J x s(2)/C(2) = kg x m(2)/C

In what unit is self inductance measured?Give the three most important equivalents.

Negative

Is the self-induced EMF of the coil positive or negative when current is increasing?

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Self induced EMF

The electric field strength at a point removed from an oscillating dipole is the resultant of a vector showing the effect of the state of charge present at one end of the dipole and the vector showing the effect of the state of charge present at the other end, these two states always being office it (if not zero). The results and always points along a line parallel to the current, toward the end of the dipole that is negatively charged. Since the charge and each and oscillates between positive and negative, the direction of the resultant showing the strength of the electric field at the point in question must oscillate also. A magnetic field appears about the dipole as a result of current in the wire. When the current is moving one way, the strength of the field at a point removed from the dipole has a direct given by Ampere's rule. When the current is moving the other way, the field reverses direction. Therefore, the point in question is exposed to a magnetic field of oscillating strength.

Show that the electric and magnetic fields at a point removed from an oscillating dipole also oscillate.

C=q/v; In words, capacitance is the amount of charge that must be packed onto each plate of the capacitor to raise the voltage across the plates by one volt.

State the definition of capacity of a negative plate both in an equation and in words.

Self conduct tends is the tendency of a loop or coil to oppose any change in its own current, whereas mutual inductance is the tendency of one coil to induce an EMF in another coil

What is the difference between self-inductance and mutual inductance?

The formula for the total inductance of two inductors in series when they affect each other is L = L1 + L2 +/- 2M. The positive sign is used if the combination is series aiding; the negative sign is used if the combination is series opposing.

What is the equation for two inductors in series with the affect each other? When M. is positive? Negative?

-Ei/delta I/delta t Where L. is the self inductance, Ei is the induced emf, and delta I/delta t is the time the rate of change in current

What is the formula for L? Identify each letter.

L=L1 + L2...; 1/L = 1/L1 + 1/L2...

What is the formula for the total inductance of coils in series? In parallel?

W(by) = I(2)RT The energy expended as heat depends upon the square of the current, the resistance, and the time.

What is the formula giving how much energy is expended in a resistance as heat? Upon what factors does this energy depend?

L = u N(2)A/l Where L is the self inductance, u is the permeability of the core, N is the number of loops, A is the cross-sectional area, and l is the length.

What is the formula giving the dependence of L on geometrical factors? Identify each letter.

The relation is given by V(ef)= V/square root of two, where V is maximum voltage.

What is the relation between V(et) and maximum voltage?

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What is the symbol for an inductor?

Sinusoidal; 60 Hz

What is the waveform of house current? What is its frequency?

A dielectric produces an electric field opposed to the electric field that exists between the plates; consequently, a dielectric weakens the repulsive forces that hinder the storage of more charge. Since the voltage associated with a given state of charge is reduced, capacitance is increased.

Why does a dielectric increase capacitance?

Since Ief equals the squaroot of I(2)/2, and since the latter quantity may be described as the root mean square of I, Ief is currently called Irms (where "RMS" stands for root mean square).

Why is I(et) also called I(rms)?

If a positive plate is positioned close to the negative plate, electrons in the negative plate rushed to the side facing the positive plate and leave room on the other side for the addition of more electrons.

Why is the capacity of a negative plate increased by the close proximity of a positive plate?

inductor

a circuit element with the property of self inductance

dielectric

a material that reduces the voltage associated with a given state of charge

Effective value

based on how much joule heat the current is capable of producing any given resistance; Specifically, an alternating current is regarded as equal in strength to the direct current that, in the same resistance, would produce heat at the same average rate

series opposing

describes an arrangement in which self inductance and mutual inductance have contrary effects

Parallel

describes an arrangement of capacitors in which a battery furnishes charge directly to both plates of each capacitor; all the plates connected to the same side of the battery received the same charge

series

describes an arrangement of capacitors in which the positive plate of the first capacitor is connected to the negative plate of the second, and so on down the line. The first and last plates are the only ones connected directly to the battery.

Series aiding

describes coils adjoined in such a way that it be self inductance in each choir is enhanced by mutual inductance due to the flux linking both coils running in the same direction

Primary

describes the changing current in the first of two coils which induces a current in the the second of two coils

secondary

describes the second of two coils in which a current is induced by the first of two coils with the changing current

in phase

describes two curves that have the same. And that are positioned so as to reach maximum, minimum, and zero values simultaneously.