FEE Flashcards - Intro to AC Circuits (3)
A signal that has the form of the sine or cosine function
Sinusoid
a sinusoidal current is usually referred to as ___
alternating current (AC)
This current reverses at regular time intervals and has alternately positive and negative values.
Alternating Current (AC)
Circuits driven by sinusoidal current or voltage sources
AC Circuits
In what ways do electricity flow
Direct Current (DC) Alternating Current (AC)
Difference between AC and DC in flow of eelctrons
DC: electrons move forward AC: Electrons switches forward and backward
Difference between AC and DC in cause of direction of elections
DC: Steady magnetism along the wire AC: Rotating magnet along the wire
Difference between AC and DC in Current
DC: Current is constant AC: Current varies with time
Difference between AC and DC in amount of energy carried
DC: Voltage cannot travel far AC: Safe to transfer over longer city distances
Difference between AC and DC in Frequency
DC: Frequency of current is 0 AC: 50 or 60Hz depending on the country
Where are AC and DC obtained from
DC: Cell or Battery AC: AC generator and mains
Passive parameters of AC and DC
DC: Resistance AC: Impedance
Power factors of AC and DC
DC: Always 1 AC: Between 0 and 1
the ratio of the real power that is used to do work and the apparent power that is supplied to the circuit.
Power Factor
Alternating voltage may be generated by?
(a) by rotating a coil in a magnetic field or (b) by rotating a magnetic field within a stationary coil
the resulting graph of an alternating current plotted to a base of time.
Waveform
It also refers to a time-varying waveform known as a sinusoidal wave or a generated sine wave.
AC Waveform
Types of Waveform
sinusoidal wave, Half wave, Triangular wave, Semi-circular wave, Trapezoidal wave, Square wave
One complete series of values
Cycle
One complete cycle is equivalent to
1 revolution
The time taken in seconds for an alternating quantity to complete one cycle
Period or Periodic Time (T)
Electromagnetic Induction formula
E(emf) = -N(dΦ/dt)
Time period formula
T = 2π/ω or T = 1/f ; ω: Angular Velocity in rad/s
Angular Velocity (ω) formula
ω = 2πf
The number of cycles completed per second
Frequency (f)
The standard frequency of the electricity supply in the Philippines
60 Hz
Frequency (f) formula
f = PN/120 or f = 1/T ; P: No. of pole/s ; N: speed in rpm ; T: Time in seconds
the voltage produced when a conductor winding in a magnetic field or by altering the direction of flux
emf
This is largest value reached in a half cycle (during positive or negative) of the waveform.
Max Value (or peak/crest value)
This is the average value measured over a half cycle
Ave Value (or mean value)
form factor formula
ff = rms/ave
peak factor
pf = max/rms
This is the current which will produce the same heating effect as an equivalent direct current
Effective (rms) value
It is sometimes called as root mean square (rms) value and whenever an alternating quantity is given, it is assumed to be the rms value
Effective value
For sine wave, form factor is equivalent to ___ while ___ for the peak factor.
1.11 ; 1.41
rms formula in sine wave
rms = max/√2
ave formula in sine wave
ave = 2max/π
the values of the alternating quantities at any instant of time or angle of rotation. They are represented by small letter.
Instantaneous values
sinusoidal voltage formula
e = Emsin(wt + θ)
sinusoidal current formula
i = Imsin(wt + θ)
