Week 2 Flashcards
T or F: Inductance is the characteristic of an electrical conductor or circuit, which opposes a CHANGE in current flow.
True
the unit of inductance is called the _______
henry
T or F: The unit for measuring inductance (L) is the henry (h)
True
Lenz’s Law
states that the induced emf in any circuit is always in a direction to oppose the effect that produced it.
T or F: XL is the opposition to AC current due to the inductance in the circuit
True
XL =
inductive reactance, measured inΩ
f
frequency, measured in Hz
L
inductance, measured in henrys
counter-emf (Cemf) or back-emf
This induced voltage is in a direction so as to oppose the supply voltage
T or F: the Cemf is acting like a resistance in reducing the current
T
T or F: The inductive reactance of a coil is the number of ohms of resistance that the coil seems to offer as a result of a Cemf induced in it. Its symbol is XL to differentiate it from the DC resistance r.
True
True or False: Terminal blocks shall be wired and mounted so the internal and external wiring does not cross over the terminals.
True
True or False: One conductor only shall be terminated on the top of the terminal block for the conductors that are outside of the control panel.
True
Alternating current (AC) control voltage shall be ______ volts or less, single phase.
120
The color _____ with or without YELLOW stripes shall be used to identify the equipment _______ conductor where insulated or covered.
Green, grounding
BLACK for Line and load circuits, AC or DC ____ volts and above.
150
______ for ungrounded AC control conductors less than 150 volts
RED
_____ for ungrounded DC control conductors
BLUE
True or False: All pushbuttons shall be mounted above or to the left of their associated stop pushbuttons.
True
What are the conductor sizes for:
1. Power circuits
2. Control circuits
- # 14 AWG
- # 16 AWG
Start button operators shall be colored ______ and of the fully guarded type
BLACK
Name the strength, or intensity, of a coil’s magnetic field depends on a number of factors:
- The number of turns of the conductor
- The amount of current flow through the coil
- The ratio of the coil’s length to its width
- The type of material in the core
Solenoid action
converts electrical energy into mechanical work through electromagnetic forces
Electromagnetic induction
It states that if a conductor cuts across lines of magnetic force, or if lines of force cut across a conductor, a voltage is induced across the ends of the conductor.
True or False: The vertical axis shows the changes in magnitude by the variations of the voltage.
True
What does the horizonal line on a graph showing a sine wave mean?
It shows time
True or False: When a conductor cuts lines of force or lines of force cut a conductor, a voltage is induced across the conductor
True
There must be ________ ________between the conductor and the lines of force in order to induce a voltage. (2 words)
relative motion
The number of cycles in a given period of time, usually one second, is termed as the ___________.
frequency
In the first half of rotation, this produces a _____ voltage and in the second half of rotation produces a _______ voltage
positive, negative
The maximum number of flux lines is being cut at ___ degrees and this is the maximum value of voltage generated.
90
