Math Review
The square root of [(5x5) + (12x12)] is
SQRT (25+144) = SQRT 169 = 13
How many alternations are in ONE cycle of an AC voltage waveform?
2
The maximum value of a sine wave occurs at which 2 angles?
90 and 270 degrees
The property of an AC circuit that opposes any change of current in the circuit is called
Inductance
The property of an AC circuit that opposes any change of voltage in the circuit is called
Capacitance
What is 1.47 kohms in ohms?
1470 ohms
A generator that produces AC is called what?
An alternator
If a 16-pole alternator is rotated at 1500 rpm, what is the output frequency?
f = (nxp)/120 = (16x1500)/120 = 200 Hz
What are the 2 types of capacitors
Polarized and non-polarized
What is the insulating material between the plates of a capacitor called?
Dieletric
In a right angle triangle, you are given the length of the adjacent as 480, length of the opposite as 360. What is the length of the hypotenuse?
600
When a 20-pole alternator has made 1 complete revolution, the voltage sine wave will have gone through how many electrical degrees?
360x10 = 3600 elec degrees
** 360 elec degrees are produced when a conductor passes by 2 opposite poles - page 7 of 030201a module **
How many times is a magnitude of 120V (neg or pos) attained in a sine wave with a 170V peak?
4 times per cycle
What do you need to be aware of when connecting polarized capacitors?
Polarity - connecting them backwards can cause them to explode
Name the 3 factors that affect capacitance
C = (kA)/d
k - dielectric constant of the material that separates the plates
A - area of the plates
d - distance between the plates
Which side of a right angle triangle will always be the longest?
Hypotenuse
What is the formula for finding the instantaneous value of voltage on an AC sine wave?
Emax x sin theta
When the effective value of a current waveform is known, which formula must be used to find the peak value?
Ipeak = Ieff x 1.414
When the armature of a coil pulls in, does the inductance decrease or increase?
Increase
The flux path (l) is shorter.
Name 2 capacitor applications
Timers
Rectifier smoothing and filtering
Power factor correction
Motor starting
Name the 3 trig functions
Sine, cosine, tangent
An AC meter reads 75A. The peak value of current is
75x1.414 = 106.05A
If the max value of an AC waveform is 350V, what is the instantaneous value at 75 degrees?
Name the 4 factors that affect the inductance of a coil
L = (N^2)(mu)(A)/l
N - number of turns of conductor in the coil
mu - permeability of the core material
A - cross sectional area of the core
l - length of the core's magnetic path
Name the 6 types of non-polarized capacitors
Air
Oil-filled
Paper (tubular)
Plastic film
Mica
Ceramic (disc)