AC Concepts
Combining fundamental frequency with only odd harmonics creates what type of waveform?
Square
Period formula
T= 1/f (if frequency is known, time can be calculated
Formula to calculate wavelength
300M / f
4 factors that affect the amount of EMF induced into a conductor
(CARS) 1. Conductor length within the mag field 2. Angle at which the conductor cuts through 3. Rate of speed at which the conductor is moved 4. Strength of the magnetic field
Formula to find harmonic frequencies
(Fundamental freq. hz ) * (# of harmonic freq) Ex: (20hz)(8(th harmonic)) = 160hz
Substitute variables to solve Vrms of an AC sine wave with a Vpk-pk of 12v
0.707 * 6
Vrms equation
0.707 * Vpk
A loop of wire is rotated in a magnetic field, What voltage is produced at the following sine wave locations? 0 degrees, 90 degrees, 180, 270, 360
0: 0V 90: Max positive volts 180: 0V 270: Max negative volts 360: 0V
2 advantages of AC over DC
1. DCV must be produced to the level required by the load. AC can use a transformer to step up or down voltage. 2. AC can be transmitted at a high voltage and low current levels, reducing power loss. DC transmits low voltage, high current which is dangerous and inefficient.
3 characteristics needed for sine wave calculations
1. Frequency 2. Period 3. Wavelength
3 things needed in order to produce an AC wave
1. Magnetic field 2. Conductor 3. Relative motion
Frequency formula
1/t (if period is known, frequency can be calculated)
How to calculate 8th harmonic of a 12kHz sine wave?
12k*8
An AC sine wave that has a (+) peak voltage of 7v and a (-) peak voltage of 7 has what peak to peak voltage?
14v
AC waveform is a plot of current or voltage which constantly changes in —- and —-
Amplitude / direction
Square waves can be both AC and —-
DC
What is the difference between AC and DC?
DC: current only flows in one direction - it may change magnitude (pulsating dc) - does NOT change polarity AC: current which constantly changes in both magnitude and polarity
—— ——- is an action that causes an EMF to be induced in a conductor or coil as it moves relative to a magnetic field
Electromagnetic induction
_____ is determined by the number of cycles that occur in one second
Frequency
—- frequency is the original frequency of a sine wave
Fundamental
—— frequencies are considered echoes of the fundamental frequency
Harmonic
How is period or time of a waveform defined?
How many seconds it takes for the wave to complete 1 cycle
As the speed of the generator increases, frequency (increases / decreases)
Increases
Units for wavelength
Meters / centimeters
Frequency is determined by
Number of cycles per second
When the conductor loop has completed one revolution, or 360 degrees, it has completed how many cycles of AC?
One. 1 rotation = 1 cycle AC
One cycle of AC consists of a —- and —- alternation
Positive Negative
An AC waveform is identified by having a —- and a —— alternation
Positive / negative
Combining fundamental frequency with all the harmonica creates what kind of waveform?
Ramp
Period of a sine wave is expressed as a decimal part of a —-
Second
T or F Square waveforms can be symmetrical or asymmetrical
True
If a conductor is moved through a magnetic field, a —- will be induced into the conductor
Voltage
The maximum value reached during one alternation is called
Vpk (peak voltage)
When determining circuit values in an AC circuit, what must be done first before making any other calculations?
Vpk and Vpk-pk must be converted to Vrms
A ____ is a physical activity that rises and falls periodically.
Wave
Abbreviation and unit of measurement for frequency
f Hz
Symbol for wavelength
lambda (λ)
