Chapter 5

Question 1

What is the equation for sinusoidal voltage? Define all terms

Answer 1

Vmcos(Wt+@)

Vm = peak voltage, W(omega) = angular frequency, @(theeta) = phase angle

Question 2

What is the equation for W(omega)?

Answer 2

W = 2pi/ T

Question 3

If you are given a sinusoidal voltage in terms of sin, what must you do? How?

Answer 3

Change it in terms of cos

sin(z) = cos(z-90)

Question 4

RMS) What is the equation for the average power?

Answer 4

V^2rms/ R

Question 5

What is the equation for Vrms?

Answer 5

Vm/ sqt2

Question 6

How do you calculate the phase angle?

Answer 6

360 x f x /\t

Question 7

If a sinusoidal voltage is given by Vcos(Wt + @), what is the corresponding phasor?

Answer 7

V/_@

Question 8

For a pure inductance does current lag or lead voltage? By how much?

Answer 8

Current lags the voltage by 90

Question 9

What is KVL in phasor form?

Answer 9

The sum of the phasor voltages equals zero for any closed path

Question 10

What is KCL in phasor form?

Answer 10

The sum of the phasor currents entering a node must equal the sum of the phasor currents leaving the node

Question 11

What is the equation for power for a pure resistance load?

Answer 11

p(t) = VmIm.cos^2.(Wt)

Question 12

What is the equation for power for a pure inductance load?

Answer 12

p(t) = VmIm/ 2.sin(2Wt)

Question 13

What is the equation for power for a pure capacitance load?

Answer 13

p(t) = -VmIm/2.sin(2Wt)

Question 14

For a pure resistance load, what phase are V and I in?

Answer 14

In phase

Question 15

For a pure resistance load, is power positive or negative? What does this mean?

Answer 15

Power is positive

Energy flows from the source to the load

Question 16

For a pure inductance load, what phase are V and I in?

Answer 16

I lags V by 90

Question 17

For a pure inductance load, is power positive or negative? What does this mean?

Answer 17

Power is both positive and negative
When power is positive, energy is delivered to the inductance source
When power is negative, inductance returns energy to the source

Question 18

For a pure capacitance load, what phase are V and I in?

Answer 18

I leads V by 90

Question 19

For a pure capacitance load, is power positive or negative? What does this mean

Answer 19

Power is both positive and negative
When power is positive, energy is delivered to the capacitance source
When power is negative, capacitance returns energy to the source

Question 20

If the reactive power is positive, what direction does it flow?

Answer 20

Source to load

Question 21

If the reactive power is negative, what direction does it flow?

Answer 21

Load to source

Question 22

What load has a positive reactive power?

Answer 22

Inductance

Question 23

What load has a negative reactive power?

Answer 23

Capacitance

Question 24

What is the equation for power for a general load?

Answer 24

P = VrmsIrms.cos(@)
@ = theeta

Question 25

What is the equation for power factor

Answer 25

PF = cos(@)
@ = theeta

Question 26

What is the power angle?

Answer 26

@v -@i

@ = theeta

Question 27

What is the equation for reactive power?

Answer 27

Q = VrmsIrms.sin(@)
Q = reactive power, @ = theeta

Question 28

What is the unit for reactive power?

Answer 28

VAR, volt ampere reactive

Question 29

What is the equation for apparent power?

Answer 29

AP = VrmsIrms

Question 30

What is the unit for apparent power?

Answer 30

VA

Question 31

What is the equation for complex power?

Answer 31

S - 1/2. VI

S = complex power, V = phasor voltage, I = phasor current