Answer ALL questions. Look for any feedback given if you get an answer incorrect. Keep choosing an answer until you get it correct. CORRECT or INCORRECT answers are indicated at the TOP of the page. A score is given at the TOP of the page when the exercise has been completed.
What voltage level is available on the secondary transformer conductors shown here, for a motor supply in an industrial workshop?
400v
400 and 230v
230v
110v
What voltage level would be utilised on the secondary transformer conductors shown here to supply the lights and sockets in a small office ?
400v
400 and 230v
230v
110v
A 3kW immersion heater is connected to a 230v AC supply. calculate the current drawn from the supply.
13A
10A
14A
12A
What is true (or real) power better known as?
W
VA
VAr
kVA
What is apparent power better known as?
W
VA
VAr
kVA
What is reactive power better known as?
W
VA
VAr
kVA
By which method is power factor improved in an AC circuit?
fitting a capacitor is series with the load
fitting a capacitor is parallel with the load
fitting an inductor is series with the load
fitting an inductor is parallel with the load
Identify the missing value (?) on the 'POWER TRIANGLE' shown here?
kW
kVA
kVAr
VA
A 12kW lighting load has a unity power factor. Calculate the value of the apparent power.
12
144
1200
12000
What is the current value in a neutral conductor of a balanced 10kW 3-phase machine with a p.f = 0.8 ?
0 amps
1.732 x 400
0.8 x 400 x 1.732
10000 / 1.732 x 400 x 0.8
Indicate the phase voltage from this diagram.
B
A
C
D
Indicate the line voltage from this diagram.
A
B
C
D
Indicate the phase current from this diagram.
D
B
C
A
Indicate the line current from this diagram.
C
B
D
A
Indicate the line current from this diagram.
A
B
A and B
C
Indicate the phase current from this diagram.
B
A
A and B
C
Indicate the line voltage from this diagram.
C
A
A and B
B
Which one of the following types of equipment does not produce large amounts of 'third harmonic' current?