Unit 16 Flashcards
Effective ac voltage or effective ac current is the equivalent value of what?
dc voltage or dc current that would produce the same amount of heat in a resistor
How do you calculate the frequency?
The number of times the rotor turns in one second
(T/F) The waveform for alternating-current circuits is asymmetrical
False
A waveform image is used to display the level and direction of _______ and ________
Current : Voltage
In an AC generator, the magnitude of the voltage produced depends on what 3 things?
1) Number of turns of wire 2) Strength of the magnetic field 3) Speed at which the coil rotates
What does RMS value stand for?
Root-Mean-Square
Less current uses bigger or smaller conductor size?
Smaller
How do you get non-symmetrical waveforms?
Combination of AC and DC wave forms
In generators that produce large quantities of electricity, why would you use an electromagnet over a permanent magnet?
When using an electromagnet you can alter that magnetic field which therefore allows you to control the output voltage
Most electricity in the US has a frequency of _____ Hz
60
The value of the ac current or voltage waveform at a moment of time is called what?
Instantaneous value
(T/F) The effects of electron movement change based on the direction of current flow
False
When two waveforms are in step with each other, they are said to be ____
In-phase
(T/F) The primary reason for using alternating current is because it’s inexpensive to transmit
True
A direct-current waveform displays the direction and _____ of the current or voltage
Magnitude
A three-phase generator has each of its windings out-of-phase with each other by ______ degrees
120
Phase differences are often expressed in degrees; one full wave from equals ______ degrees
360
What is the best way to know which waveform is leading or lagging?
Find out which waveform finished its cycle first
When describing the relationship between voltage and current, the reference waveform is always ______
Voltage
An alternating-current waveform displays the level and direction of the current and voltage for every instant of time for how many revolutions of the rotar?
One
“Phase” is a term that indicates the _____ or ______ relationship between two waveforms.
Time : Degree
When a magnetic field moves through a coil of wire, what causes the electrons in the wire to flow in a specific direction?
Lines of force of the magnetic field
Electrons flow only when there is motion of the conductors relative to the ______ _____
Magnetic Field
In generators that produce large quantities of electricity, which of these is stationary and which of them is not? Conductor Coils and Magnetic Field
The conductor coils are stationary and the magnetic field revolves within the coils
The maximum value the ac current or voltage waveform reaches is called what?
Peak Value
For a pure sine wave:
Effective value = RMS value
What are two ways to express frequency?
Hertz or Cycles per second
A nonsinusoidal waveform is created when nonlinear ____ distort the sine wave
Loads
