Phasors

Question 1

Calculate the peak to peak voltage (Vptp)and rms voltage (Vrms)

Answer 1

Vptp = 2 x Vp
Vrms = Vp / sqrt(2)

peak voltage (Vp)

Question 2

sinusoidal current equation

Answer 2

i(t) = Asin(ωt + φ)

amplitude (A)
angular frequency (ω)
phase angle (φ)
time (t)

Question 3

frequency

Answer 3

f = ω / 2π

angular frequency (ω)

Question 4

The phaser representation in polar and rectangular form

Answer 4

polar form:
V = Vrms / φ

rectangular form:
V = Vrms cos(φ) + j Vrms sin(φ)

phase angle (φ)

Question 5

Draw the phasor diagram

Answer 5

• use the polar form Vrms / φ
• draw a straight line of length Vrms with the angle φ to the horizontal

phase angle (φ)

Question 6

What does Vrms

Answer 6

root mean squared current/voltage

Is the DC equivalent current to AC
DC power = Average AC power

Question 7

Average AC power over one period

Answer 7

P = I^2 R / 2

Question 8

Average AC power over one period

Answer 8

P = I^2 R / 2

Question 9

Explain the lead and lagging of phasors of two signals

Answer 9

•If one is ahead of the other signal by an angle φ then we say that the first signal leads the second one by angle φ
•If one is behind the other signal by an angle φ then we say that the first signal lags the second one by angle φ

Question 10

The division and multiplication of phasors

Answer 10

Multiplication:
= V1V2
= V1< θ1 x V2 < θ2
= V1V2 < (θ1 + θ2)

Division:
= V1 / V2
= V1< θ1 / V2 < θ2
= V1/V2 < (θ1 - θ2)

Question 11

The addition and subtraction of phasors

Answer 11

• convert to rectangular form
• perform simple calculations
• then convert back to appropriate form