CIRCUITS 2 Flashcards
current and voltages are represented by magnitude and direction.
AC Circuit
sinusoidal voltage and current are selected because:
- low iron and copper losses
- less interference
- less disturbance
voltage that changes its polarity and magnitude at regular interval of time.
alternating voltage
direction of the current is changed and the magnitude of current changes with time.
alternating current
The maximum positive or negative value attained by an alternating quantity in one complete cycle
Amplitude
One half cycle (180 degrees electrical)
Alternation
one set of positive and negative values completes by an alternating quantity or it goes through 360 degrees
Cycle
value of voltage or current at any instant of time, denoted by (i or e)
Instantaneous Value
number of cycles made per second by an alternating quantity. It is measured in cycle per second (c/s) or hertz (Hz) and is denoted by (f)
Frequency
time taken in seconds by a voltage or a current to complete one cycle
Time Period
shape obtained by plotting the instantaneous values of an alternating quantity such as voltage and current along the y axis and the time (t) or angle (𝜃 = 𝜔𝑡) along the x axis
Wave Form
Types of Periodic Waveform:
1) Sine Wave
2) Triangular Wave
3) Complex Wave
4) Square Wave
RMS
Root Mean Squared
ratio between the average value and the RMS value
Form Factor
ratio between the R.M.S. value and the Peak value
Crest Factor
time-varying periodic waveforms with parameters including voltage and frequency
Sinusoidal Alternating Waveforms
periodic waveforms whose shape can be plotted using the sine or cosine function from trigonometry
Sinusoidal waveforms
it is this basic principal that electrical machines and generators use to generate a Sinusoidal Waveform for our mains supply.
Electromagnetic Induction
to convert a mechanical energy such as rotation, into
electrical energy, a Sinusoidal Waveform
Faraday’s electromagnetic induction
The amount of EMF induced into a coil cutting the magnetic lines of force is determined by the following 3 factors:
1) Speed
2) Strength
3) Length
the speed at which the coil rotates inside the magnetic field.
Speed
the length of the coil or conductor passing through the magnetic field.
Length
the strength of the magnetic field.
Strength
the velocity at which the generator rotates around its central axis determines the frequency of the sinusoidal waveform and which can also be called
angular velocity, ω
used to describe the difference in degrees or radians when two or more alternating quantities reach their maximum or zero values
Phase Difference
is the exact opposite to the series circuit
Parallel RLC Circuit
“the total current entering a junction or node is exactly equal to the current leaving that node”.
Kirchhoff’s Current Law,
are added together in parallel branches, whereas
impedances are added together in series branches.
Admittances
reciprocal of impedance
Admittance (Y)
reciprocal of resistance
Conductance (G)
reciprocal of reactance
Susceptance (B)
In AC circuits, it is defined as the ease at which a circuit composed of resistances and reactances allows current to flow when a voltage is applied taking into account the phase difference between the voltage and the current.
Admittance (Y)
is defined as the ease at which a resistor (or a set of resistors) allows current to flow when a voltage, either AC or DC is applied.
Conductance (G)
In AC circuits, it is defined as the ease at which a reactance (or a set of reactances) allows an alternating current to flow when a voltage of a given frequency is applied.
Susceptance (B)
has a horizontal conductance axis, G and a vertical susceptance axis, jB
admittance triangle
to calculate the magnitudes of all three sides as well as the phase angle
Pythagoras
