EE1F25- Wave theory Flashcards
(16 cards)
Define:
Amplitude
Cycle
Period
Frequency
Amplitude- Maximum deviation of the function from its centre position
Cycle- Repeating portion of a function
Period- Duration of a cycle
Frequency- Inverse of a period f=1/T
Define the RMS/effective value of an alternating quantity?
The value of direct current which when flowing through a given resistance of for a given time produces the same heat as produced by the alternating current when flowing through the same resistance
Define these quantities for sinusoidal voltages/currents
v=
Vm=
f=
w=
v= Vmsin(wt)
Vm= is the peak voltage
f= frequency in Hz
w= angular frequency in radian per second, specifies how many oscillations occur in a unit time interval
Harmonics: How can non-sinusoidal periodic voltages and currents be expressed?
Can be expressed as the sum of sine waves in which the lowest frequency is f and all other frequencies are intergral multiples of f.
What must quantities contain to be a harmonic quantity?
Any quantity that contains multiple frequencies is a harmonic quantity
What is the fundamental frequency?
The frequency of which others have been expressed as multiples of is the fundamental frequency
What makes an odd and even harmonic?
An odd multiple of the fundamental is an odd harmonic whereas an even multiple of the fundamental is an even harmonic
How do we attain a RMS/Effective value?
-First obtaining the square of the RMS value of each term (dividing by root 2, then squaring)
-Adding the obtained sqaured rms values
-Taking the square root of the sum
What do phasors represent?
Phasors are used to represent sinusoidal quantities to avoid drawing the sin waves
How are characteristics represented in phasors?
-The length of a line is proportional to the rms voltage or current it represents
-To show the phase angle or phase displacement between voltages and currents the phasors bear an arrow
What is a phase angle in a phasor?
The phase angle is the angle through which one of them has to be rotated to make it point in the same direction as the other
When are two phasors said to be in phase?
The phase angle between them is zero
How is the sum of sinusoidal quantities achieved?
Obtained by taking the vector sum of their phasors
How is the difference of sinusoidal quantities achieved?
First reverse the subtracted quantity and add as a vector to other phasors
What is the condition for adding/subtracting sinusoidal quantities?
Only sinusoidal quantities of the same frequency can be added or subtracted
