Question 1
Question
Which of the following formulas can calculate power in an ac circuit?
Answer

P = V x I x pf

P = V + I

P = V x I

P = V/R
Question 2
Question
What is the power produced by a 400v three phase system which delivers 25A at a power factor of 0.85
Question 3
Question
What is the power produced by a 400v three phase system which delivers 10A at a power factor of 0.7
Answer

4849.6W

4.7kW

5000W

4700W
Question 4
Question
The power factor of an installation can be calculated from
Answer

Cosθ = Z/X

Cosθ = X/Z

Cosθ = KVA/KW

Cosθ = KW/KVA
Question 5
Question
The power factor of an inductive load can be improved by?
Answer

Connecting a inductor across the load

Connecting a resistor in parallel with the load

Connecting a capacitor in series with the load

Connecting a capacitor across the load (parallel)
Question 6
Question
The power factor of a load consisting of inductance and resistance can be calculated from
Answer

Cosθ = True Power/Apparent Power

Cosθ = Apparent Power/ Reactive Power

Cosθ = Reactive Power/True Power

Cosθ = Apparent Power/True Power
Question 7
Question
The formula required to calculate the total power of a single phase inductive load supplied by an a.c. supply is
Answer

P = IV sinθ

P = IV

P = IV tanθ

P = IV cosθ
Question 8
Question
If the W is 100 and the VA is 120 what would the power factor be
Question 9
Question
If the kW is 200 and the KVA is 400 what would the power factor be?
Question 10
Question
A single phase circuit draws a current of 21.7A from a 230 V circuit at a power factor of 0.4
What is the current drawn if the power factor is corrected to 0.85
Answer

18.4 A

23.4 A

10.21 A

21.7 A
Question 11
Question
A circuit dissipates 2000 W at a power factor of 0.5 when connected to a 230 V ac supply. The current drawn from the supply is
Answer

17.8 A

17.39 A

4.3 A

8.7 A
Question 12
Question
A circuit dissipates 1.5 kW at a power factor of 0.75 when connected to a 230V ac supply. The current drawn from the supply is
Question 13
Question
A three phase system gives the following readings
kVA =30 kW= 45
What is the power factor for the system
Question 14
Question
A three phase system gives the following readings
kW= 400 kVA = 500
What is the power factor for the system
Question 15
Question
What unit is reactive power measured in
Question 16
Question
What unit is apparent power measured in
Question 17
Question
What unit is true power measured in
Question 18
Question
Which component would cause the current and voltage to behave as above
Answer

resistor

rectifier

capacitor

Inductor
Question 19
Question
Which component would cause the current and voltage to behave as above
Answer

Inductor

capacitor

resistor

rectifier
Question 20
Question
Which component would cause the current and voltage to behave as above
Answer

Inductor

capacitor

resistor

rectifier