Latest 2024 Approved by Experts Graded A++
when a cam or vane is moved close to a magnetic levleing switch what occurs?
the switch changes its satate
what is meant by the normal state of relay contacts?
contact state without current applied to the coil
what type of wave form is generated by two pole ac generator in one complete
revolution?
one full AC cycle
what defines the the period of a ac waveform ?
the time it takes to complete one full cycle .
what is the period of a 120 hz
.00833 seconds
a sine wave beginning at 0 degrees will reach positive and negative peaks at what
two points ?
90 and 270 degrees
what is it meant by the term peak to peak voltage ?
voltage between positive and negative peaks
the expression 0.636Xpeak voltage best describes what?
voltage or current average
what best describes the term AC effective voltage ?
the AC voltage required to produce the same power as a DC voltage
what is the peak voltage of a waveform with 480 VAC RMS?
679 volts
what effect an inductor has on current flow ?
it opposes change
what is the secondary voltage of a 5 to 1 step down transformormer whith a
primary voltage of 125 volts
, 25 volts
the primary of a 5 to 1 step down transformer has 1 amp . what is the secondary
current?
5 amps
how can three phase voltage be stepped down using transformer ?
by using a three phase transformer or three single phase transformers
in capacitors , what is the purpose of the dielectric ?
prevent acring within the capacitor
which of the following is true about capacitors in ac CUIRCUITS .?
current leads voltage all the time
what describes a capacitor's ability to store an electrical charge
capacitance
what is the time constant for a circuit with 150 k ohms and 2 microfarad
capacitor?
.3 seconds
what describes a capacitor's ability to store an electrical charge
capacitance
which of the following satements is correct about polorized electrolytic
capacitors
voltage polarity must be correct
what happends in a cuircuit , when the capacitor voltage equals the source
voltage ?
current flow stops in the cuircuit
in a dc cuircuit when capacitors are present , when is current maximum ?
the instant when power is applied
if a cuircuit has a capacitor of 5 micro farads and a source voltage of 120 volts DC
through a resistant of 200 k , how long will it take to fully charge?
5 seconds
what is the definition of a time constant of a capacitor ?
the time it takes for the capacitor to charge to 63.2 % of fthe applied voltage
which unit of measure is used to measure capacitance ?