In a direct current system the supply voltage must be generated at the level required by the load
True
The points of maximum attraction are called
Magnetic Poles
There are three fundamental conditions that must exist before a voltage can be produced by magnetism.
One, there must be a conductor in which the
voltage can be produced.
Two, there must be a magnetic field in the
conductor's vicinity.
Three, there must be relative motion between the
field and the conductor.
The direction of is related to the direction of movement of the conductor through the magnetic field.
current flow
The electron movement is first in one direction, then in
the other
SINE WAVE
True/False
The voltage generated by the angular motion of a
conductor through a magnetic field describes a sine wave
True
IN a Sine Wave, each 30° position describes not only the path of the conductor rotating in a two-pole field but the instantaneous values of at each position
voltage induced
True/False
The effective value of 1.414 peak AC amps is 1 amp DC, therefore the effective value of 1 peak AC amp is 0.707 amps DC
True
When the voltage or current rises from zero value to maximum and back to zero, it is called an
alternation
A sine wave describes 2 complete in 360°. A cycle is defined as two in a period of time.
alternations, alternations
Frequency is measured in cycles per second or HERTZ. Typically, the frequency of power systems in North America is
60 hertz
What are some advantages of three-phase power
over single-phase power
Generators operate more efficiently and have better regulation
generating three-phase power.
The transmission of power is cheaper due to the use of 25% less conductor material.
Three-phase motors are superior to single phase motors in cost and operating characteristics.
Ohm's law that states that current is directly proportional to
applied voltage
True/False
If AC voltage is applied to a resistance, the resultant current will be a sine wave
True
When two waves are precisely in step with one another they are said to be
IN PHASE
Waves do not go through their maximum and minimum points at the same instant of time, the waves are said to be
OUT OF PHASE
To further describe the phase relationship between two waves, the terms LEAD and LAG are used. The amount by which one wave leads or lags another is measured in
degrees
True/False
It is possible for one wave to lead or lag another by any number of degrees, except zero or 360
True
Total opposition to current flow in an AC circuit is called
IMPEDANCE
True/False
It is the impedance of an AC circuit that may cause the voltage or current to be out phase with each other.
True
What are the oppositions to current in an AC circuit
RESISTANCE, CAPACITIVE REACTANCE, and INDUCTIVE REACTANCE
True/False
In a DC circuit, the net opposition to current flow in a circuit is
composed of only one electrical value -- RESISTANCE
True
The opposition to current flow that is produced merely by a
conductor's inability to perfectly conduct current is resistance
Resistance
The transfer of energy through the electrostatic field surrounding the conductor is known as
CAPACITANCE
True/False
The greater the "rate of change" in voltage, the greater the capacitance on the circuit
True
True/False
In capacitive circuits, current leads voltage
True
True/False
In an inductive circuit, the current leads the applied voltage
False - lags
The transfer of energy through the electromagnetic field surrounding the conductor is known as
Inductive Reactance
During the out-of-phase periods, the product of the Voltage and Amps produces a negative value. This portion of the circuit is known as .
Reactive Power or VAR (Volt Amperes Reactive)
True/False
VAR is the portion of the circuit's energy that is
used to support electromagnetic and/or electrostatic fields
True
The product of the applied voltage and the total
circuit current ( I× E)
Apparent Power
The product of apparent power and power factor
True power
True/False
True Power is the product of the applied voltage and the portion of the circuit current that are "in-phase" with the voltage.
True
The energy that reacts to changes in the circuit
Reactive Power (VAR)
VAR is the product of the applied voltage and the portion of the circuit's current that is with the voltage
"out-of-phase"
True/False
The current flowing in one winding of a DELTA-connected transformer are less than the current flowing on the one phase of the line supplying the bank
True
True/False
Bank ammeters read the phase current of the circuit.
True
One of the benefits of a DELTA system is that one phase of a three phase bank can be removed and operated . The capacity of the bank is reduced to approximately ; however, the three-phase system can continue to operate.
OPEN DELTA, 58%
True/False
The current flowing in one phase of a WYE connected bank is the
same as the current flowing in the line supplying the bank
True
The voltage across one winding of a WYE connected transformer is always the line voltage of the supply circuit
less than
Generally the voltmeters on a power bank convert voltage to voltage. Therefore; Meter volts = line volts
phase, line
Any physical quantity that has both magnitude and direction, such as force or velocity, is called a .
