ECS Electrical Supply Systems and Distribution

Question 1

What is the standard nominal voltage for a single-phase domestic supply in the United States?

Accepted Answer

120V

Answer

110V

Answer

208V

Answer

240V

Question 2

In a three-phase electrical supply system, what is the phase angle between each of the three phases?

Accepted Answer

120 degrees

Answer

90 degrees

Answer

180 degrees

Answer

360 degrees

Question 3

What type of transformer connection is most commonly used to supply three-phase power to commercial buildings in the US?

Accepted Answer

Delta-Wye

Answer

Delta-Delta

Answer

Wye-Wye

Answer

Wye-Delta

Question 4

What is the primary purpose of a main distribution board (MDB) in an electrical installation?

Accepted Answer

To distribute power to sub-circuits and provide overcurrent protection

Answer

To measure electricity consumption

Answer

To convert AC power to DC power

Answer

To regulate voltage fluctuations on the supply

Question 5

Which of the following best describes a 'radial circuit' in electrical distribution?

Accepted Answer

A circuit where power flows in one direction from the supply to the final outlet

Answer

A circuit that loops back to connect to the supply at both ends

Answer

A circuit that distributes power in a ring around the building

Answer

A circuit designed only for three-phase loads

Question 6

What is the function of a neutral conductor in a single-phase AC supply?

Accepted Answer

To provide a return path for the load current back to the supply

Answer

To carry fault current to earth during a short circuit

Answer

To protect equipment from voltage surges

Answer

To regulate the frequency of the supply

Question 7

What does the term 'demand factor' refer to in electrical distribution planning?

Accepted Answer

The ratio of maximum demand to the total connected load

Answer

The ratio of actual power consumed to apparent power

Answer

The efficiency rating of the distribution transformer

Answer

The percentage of voltage drop across the distribution cable