Deck 9: Electrical Installations

Question 1

What is a low power factor?

A)0.8 and below
B)Zero
C)0.95
D)0.85
E)1

Answer 1

A

Question 2

How is plant protected by an MCB?

A)Building management computer system detects faults and trips main circuit breaker to the plant room where a fault occurred
B)MCB means manual circuit breaker switch at a distribution board
C)Micro circuit breaker switch opens on detecting excess current
D)MCB means moulded case breaker cartridge fuse for each plant circuit at main switchboard
E)It is a thermal overload switch

Answer 2

C

Question 3

What are photovoltaic cells used for on buildings?

A)Never used as uneconomic embellishment
B)On-site electricity generation with alternating current rectifiers, battery storage and often used to meet some of the artificial lighting continuous demand
C)Alternative to roofing material
D)Charging 12 volt emergency power supply batteries, UPS
E)To make a public statement about this building's sustainability credentials.

Answer 3

B

Question 4

What is the meaning of inverter drive?

A)Motor driven at variable alternating current frequencies
B)An electric motor installed in an inverted position
C)Three phase electric motor
D)Three phase motor running in single phase
E)Digitally driven motor

Question 5

How is power consumed by an electrical item measured?

A)Voltmeter connected into line conductor to the load and an ammeter connected in parallel with the load
B)Wattmeter cut into the line conductor
C)Voltmeter and current meter both cut into line conductor to the load
D)Ammeter connected into the line conductor to the load and a voltmeter connected in parallel with the load
E)Wattmeter connected in parallel with the load

Question 6

Which system of public electricity is provided to small to medium sized non-domestic buildings in the UK and Australia?

A)210 volt,1 phase, 55 Hz, alternating current
B)50 Hz, 240 volt, AC
C)AC, 50 Hz, 3 phase, 415 volt
D)2 phase, 60 Hz, 200 volt
E)440 volt, 3 phase, 60 Hz

Question 7

How is three phase electricity created at a power station?

A)Each alternator has three stator coils so one revolution of the rotor generates three separate sine wave outputs
B)Three single phase alternators have interconnected output power circuits
C)Single phase generators with rectifiers creating three phases
D)Multiple transformers create three phases
E)Three single phase alternators each power one line voltage; each building takes all three lines to have three phase power

Question 8

Which of these does a single phase electricity current look like on an oscilloscope screen? (Hint, draw them.)

A)Zero phase angle maximum positive current, 90^o phase angle zero current, 180^o phase angle maximum negative current
B)Zero phase angle zero current, 90^o phase angle maximum positive current, 180^o phase angle zero current
C)Zero phase angle 50% maximum positive current, 90^o phase angle 100% positive current, 180^o phase angle zero current
D)135^o phase angle zero current, 225^o phase angle maximum negative current, 315^o phase angle zero current
E)Zero phase angle zero maximum negative current, 90^o phase angle zero current, 180^o phase angle maximum positive current

Question 9

Which correctly describes the relationship between voltage and current in an alternating current system?

A)Inefficient generators produce a current flow lagging voltage
B)Voltage and amperes are synchronised
C)Voltage peak occurs behind peak value of current
D)Current always follows voltage producing it by exactly one phase
E)Current always follows fractionally behind the voltage that produces flow of electricity

Question 10

What opposes flow of electrical current into an electric motor?

A)Mechanical feed-back from forces on motor output shaft
B)Resistance of the motor coils
C)Temperature coefficient of resistance increases circuit electrical resistance
D)Inductance
E)Capacitance of motor control system