Sources Transformation - AC Circuits Flashcards
an ideal voltage source in series with an internal resistor, Rs
Practical Voltage Source
an ideal current source in parallel to an internal resistor Rp
Practical Current Source
if two practical sources produces the identical values of voltage (Vl) and current (Il) when they are connected to a identical values of Rl
Equivalent Practical Source
An independent voltage source in series with a resistance, or an independent current source in parallel with a resistance, delivers a maximum power to load resistance Rl for which Rl=Rs
Maximum Power Transfer Theorem
maximum power formula:
Pmax = Vs^2/4Rs = Vth^2/4Rth
a signal that has the form of the sine or cosine function
Sinusoid
- usually referred to as alternating current (ac)
- a current that reverses at regular time intervals and has alternately positive and
negative values
Sinusoidal current
circuits driven by sinusoidal current or voltage sources
AC Circuits
the angular frequency in radians/s
omega (w)
the argument of the sinusoid
omega(t) [wt]
the amplitude of the sinusoid
Vm
period of sinusoid
T
The reciprocal of this quantity is the number of cycles per second, known as…
cyclic frequency f
phase
null sign
A ____________may be used to relate or
compare sinusoids as an alternative to using the
trigonometric identities. Also, can be used to add
two sinusoids of the same frequency when one
is in sine form and the other is in cosine form.
graphical approach/graphical technique
frequency formula
f = 1/T
period formula:
T = 2(pie)/omega
a complex number that represents the amplitude and phase of a sinusoid
Phasor
rectangular form of phasor
z = x + jy
polar or exponential form of phasor
z = r∠∅ = re^j∅
is thus the phasor representation of the sinusoid v(t).
V
complex conjugate
z∗ = x − jy = r∠ − ∅ = re^−j∅
time domain representation
v(t) = Vm cos(ωt + ∅)
phasor domain representation
V = Vm∠∅
the instantaneous or time domain representation
v(t)
the frequency or phasor domain representation.
V
time dependent
v(t)
phasor
V = RIm∠∅
The ______________ of a circuit is the ratio of the phasor voltage V to the phasor current I, measured in _____________
impedance Z, ohms (Ω)
It represents the opposition that the circuit exhibits to the flow of sinusoidal current.
impedance
The ___________ is the reciprocal of impedance, measured in ____________
admittance Y, siemens (S).
The ________of an element (or a circuit) is the ratio of the phasor current through it to the phasor voltage across it,
admittance Y
