PC - Professional Electrical Contractor General Theory and Calculations Questions and Answers

Question 1

A 240-volt, single-phase circuit supplies a load that draws 30 amperes.
The circuit conductors are 150 feet long and are made of copper.
What is the approximate voltage drop on this circuit? (Use K=12.9 for copper)

Accepted Answer

7.7 volts

Answer

3.6 volts

Answer

5.8 volts

Answer

9.2 volts

Question 2

In a series-parallel circuit, three resistors are configured as follows: R1 (10 ohms) is in series with a parallel combination of R2 (20 ohms) and R3 (30 ohms). If the circuit is connected to a 120V source, what is the total current flowing from the source?

Accepted Answer

5.45 A

Answer

12.0 A

Answer

10.9 A

Answer

3.75 A

Question 3

What is the apparent power (in kVA) of a three-phase motor with a line voltage of 480V, drawing a line current of 60A?

Accepted Answer

50.0 kVA

Answer

28.8 kVA

Answer

41.5 kVA

Answer

83.1 kVA

Question 4

A single-phase transformer has a primary voltage of 480V and a secondary voltage of 120V. If the primary winding has 800 turns, how many turns are in the secondary winding?

Accepted Answer

200 turns

Answer

3200 turns

Answer

400 turns

Answer

100 turns

Question 5

Which of the following is the correct formula to calculate power (P) in a DC circuit when voltage (E) and resistance (R) are known?

Accepted Answer

P = E² / R

Answer

P = I² * R

Answer

P = E * I

Answer

P = E / R

Question 6

A balanced three-phase load has a true power of 25 kW and a power factor of 0.85. What is the apparent power of the load?

Accepted Answer

29.41 kVA

Answer

21.25 kVA

Answer

25.00 kVA

Answer

32.75 kVA

A 240-volt, single-phase circuit supplies a load that draws 30 amperes.The circuit conductors are 150 feet long and are made of copper.What is the approximate voltage drop on this circuit? (Use K=12.9 for copper)

A 240-volt, single-phase circuit supplies a load that draws 30 amperes.
The circuit conductors are 150 feet long and are made of copper.
What is the approximate voltage drop on this circuit? (Use K=12.9 for copper)