Alternating Current CH 3
Fifty microfarads = _ farads
.000050
The average value of alternating current is calculated by multiplying _ by the peak value
.637
The RMS value of AC is _ times the peak value
.707
A rotating generator having four poles and turning at 1800 RPM will generate an AC with a frequency of _ Hertz
4/2 = 1800/60secs X = 60
The AC power used in most aircraft is _ hertz
400
The frequency of most house current in the USA is _ hertz
60
The phase angle between the current and the voltage in a purely inductive circuit is _
90 degrees
An _ is one half of an AC cycle
Alternation
The time constant of a capacitive circuit is determined by the _ and the _ of the circuit
Capacitance Resistance
The opposition to the flow of alternating current caused by a capacitor in a circuit is known as
Capacitive reactance
A _ is one complete sequence of voltage or current changes from zero to a positive peak to zero, then through a negative peak, and back to zero
Cycle
The working voltage of a capacitor is rated in _ volts
DC
Increasing the inductance of a coil will _ the amount of AC that can flow through it
Decrease
When a large amount of capacity is needed with a low working voltage, a _ capacitor is used
Electrolytic
The number of complete cycles per second is the _ of AC and is expressed in _
Frequency Hertz
The total opposition to the flow of alternating current is called
Impedance
Two advantages of alternating current over direct current are
It is easy to generate It is easy to change voltage and current values
In an R-C circuit, changes in current _ changes in voltage
Lead
A capacitor with a thin dielectric has _ capacity than the same capacitor with a thick dielectric
More
The amount of induction in a coil is affected by the:
Number of turns in the wire spacing between the turns number of layers of winding ratio of the diameter of the coil to the length material used for the core
The formulas for finding total series capacitance are the same as those used for finding the total resistance of resistors connected in _
Parallel
The time required for one cycle of events to occur is known as the _ of alternating current
Period
The ratio between the true power and the apparent power in an AC circuit is known as the _
Power factor
Three types of opposition to the flow of alternating current are
Resistance Inductive reactance capacitive reactance
The waveform of alternating current produced by a rotating generator is called a _ wave
Sine
The time constant of an R-L circuit can be found using what formula?
TC = L/R
The three variables that affect the capacity of a capacitor are
The area of the plates The distance the plates are apart The dielectric constant of the dielectric
True power in an AC circuit is expressed in terms of _
Watts
Inductive reactance is indicated by the symbol
XL
In an AC circuit the product of the voltage and the current is the _ _ and is expressed in _
apparent power volt amps
Inductance opposes a change in current by the generation of a _ _
back voltage
An _ is a type of inductor installed in a circuit to impede the flow of AC of a particular frequency, while not affecting the flow of AC below that frequency
choke
A capacitor consists of two _ separated by an _
conductors dielectric
Phase angle is the angle whose _ is the power factor
cosine
Capacitive reactance _ as the frequency of the circuit increases
decreases
The total reactance is the _ the inductive and the capacitive reactance
difference
Another name for the RMS value of AC is the _ value
effective
Electrical energy is stored in a capacitor in _ fields
electrostatic
The basic unit of capacitance is _
farad
Inductance is measured in _
henries
Inductive reactance _ as the frequency increases
increases
The opposition to current flow in a conductor caused by the generation of a back voltage as the magnetic field cuts across the conductor is called
inductive reactance
In a purely inductive circuit, the current _ the voltage
lags
Inductive reactance is measured in
ohms
A purely resistive circuit has a power factor of
one
The reference dielectric is air which has a dielectric constant of _
one
The maximum value of voltage in either the positive or negative direction is known as the _
peak
The maximum difference between the positive and negative peak values of alternating voltage or current is called the _ value
peak to peak
Power factor is the ratio of the _ of the circuit to the impedance
resistance
Apparent power is the product of the source voltage times the
total current
An _ is used to step up or step down an AC voltage
transformer
True power may be found using the formula _
true power / apparent power = power factor
The strength of an electrostatic field is determined by the _
voltage
True power is measured in
watts
The power factor of a purely inductive circuit is
zero
