AC Electricity
Resonance
A frequency in an given RLC AC circuit at which the capacitive reactance is equal to the inductive reactance
AC Average Voltages
The averaging of all the values along the time axis with time being in full period
Variable Caps
change capacitance by changing area of plate (Dielectric in variable cap is usually air)
How many degrees of rotation are there in one cycle of AC?
360 degrees
Capacitor
A device used to store electrical energy in the form of electrostatic fields. A capacitor is essentially two conductors separated by an insulator
Name three common AC wave forms
Sine Wave Square Wave Rectangle Wave
How many alterations are there in a cycle of AC?
2 alternations
What is the period for an AC waveform with a frequency of 400 Hz?
2.5ms
How many cycles of AC are there in 400 Hz?
400 cycles
What is the frequency of AC that has a period of 1/60 per second
60 Hertz
Amount of time required for capacitor to charge to
63.2 of max "E" T=RC
What is the effective voltage of AC that has a peak value of 100 volts?
70.7V
How many times will current change/reverse direction in an AC waveform that has a frequency of 400 Hz?
800 times
How many degrees of phase difference exist between voltage and current in an AC circuit that is purely capacitive?
90 degrees leading
Farad
A basic unit of capacitance. A capacitor of one farad will hold one coulomb
AC Cycle
A complete negative and positive wave of alternating current
Hertz
A unit for measuring the frequency of vibrations or of AC electricity
Capacitor blocks DC while passing
AC
Inductor
An inductor is a passive electronic component that stores energy in the form of a magnetic field
Inductive Reactance
An opposition to the flow of AC caused by generation of an induced voltage whose polarity is opposite to that of the voltage that created it
State Ohms law for an AC circuit
Current in an AC circuit is directly proportional to voltage and inversely proportional to impedance
How many degrees of phase difference exist between voltage and current in an AC circuit that is purely inductive?
Current lags voltage by 90 degrees
AC Effective Voltages
DC voltage that would produce the same amount of heat in a resistor
Permittivity is called
Dielectric constant
Define AC
Electricity that continuously changes in magnitude and periodically in direction
Capacitor uses
Filtering AC Smoothing DC ripple Electrical coupling in radio circuits Tuning Timing Circuits
Two types of caps
Fixed caps Variable caps
Cap materials
Glass, ceramic, plastic film, air, vacuum, paper, mica, and oxide layers
Does current lead or lag voltage in an AC circuit that is purely inductive?
Lags
Does current lead or lag voltage in an AC circuit that is purely capacitive?
Leads
Does current lead or lag voltage in an AC circuit that is purely resistive?
Neither, they are in phase
What factors affect the inductance of an inductor?
The number of turns in the coil, the diameter of the coil, coil length, and material used
Apparent Power
The product of RMS current and RMS voltage expressed in volt-amperes
Reactance
The relative difficulty with which magnetic domains can be aligned and the opposition to magnetic flux
Henry
The standard unit of inductance. It is the amount of inductance in which a current change of one ampere per second will induce a voltage of one volt
RMS
The value of direct current equivalent to an alternating current sine wave
Impedance
The vector sum of the opposition to the flow of AC caused by circuit resistance, capacitive reactance, and inductive reactance
Sinewave
The wave form of AC produced by a rotary generator. Its amplitude id proportional to the sine of the angle through which the generator is turned
Induction
The wireless transfer of energy
What is the relationship between capacitive reactance and inductive reactance in a resonant AC circuit?
Their relationship depends on their phase. The phase relationship between voltage and current in an AC capacitance circuit is the exact opposite to that of an AC inductance circuit
What is the purpose of a capacitor?
To store electrical energy in an electrostatic field
In an AC circuit a capacitor drops voltage and shifts the phase of current
but does not consume power or produce heat
(True or False) Apparent Power equals True power in a resonant AC circuit
True
One farad is the capacity required to hold one coloumb of electricity under
a force of one volt
electrolytic capacitor uses liquid or paste as dielectric layer when
a large amount of capacitance is required in a small physical size
The two metal plates in a conductor are superheated by a
dielectric layer
A cap is inversely proportional to the distance between its plates and
directly proportional to the size of its plates
Amount of capacitance a capacitor has is determined by the
distance between the plates size of plates dielectric type
Capacitive Reactance
is a measure of a capacitor's opposition to AC
Dielectric Permittivity is
the ease at which electrostatic lines of force can exist in an insulating material compared to a vacuum
True Power
the power that actually exists in an AC circuit. It is the product of voltage, current, and power factor or is the product of the voltage and the current that is in phase with that voltage
Frequency
the rate at which a cycle occurs or is repeated over a particular period of time or in a given sample
Power Factor
the ratio of the resistance of an electrical circuit to the circuit impedance measured by a wattmeter and in AC, the ratio of apparent power to true power