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WorksheetsICIT Revision D
Total questions: 20
Worksheet time: 10mins
Which one of the following provisions is to enable proper functioning and control of current-using equipment for installation user?
Isolation
Functional switching.
Emergency switching.
Switching off for mechanical maintenance.
The transformer used for distribution is 3-phase 4-wire system with star point connected to earth is
Delta-Delta Step-Down Transformer
Delta-Star Step-Down Transformer
Star-Star Step-Down Transformer
Star-Delta Step-Down Transformer
In Singapore, the voltage between any two phases is 400V, 50 Hz and between any phase and the neutral is
230V, 50 Hz.
240V, 50 Hz.
230V, 60 Hz.
240V, 60 Hz.
Small non-domestic consumers, like flatted factories having industrial
loads are supplied with a 3-phase, 4-wire service cable to provide 230 V,
50 Hz single-phase and
400 V, 50 Hz three-phase.
415 V, 50 Hz three-phase.
400 V, 60 Hz three-phase.
415 V, 60 Hz three-phase.
In order to balance the three phases system, consecutive services are connected to different phases and neutral in turn to
reducing the current in the neutral
so keeping the running costs up
increasing the current in the phase
increasing the current in the neutral
The maximum electricity supply capacity for single-phase 230 V, 50 Hz provided by SP Services Ltd (SPSL) is
15 kVA
23 kVA
45 kVA
75 kVA
As in distribution system, it is important that the load currents are equally divided over the three phases to
improve the power factor
reduced the voltage drop on conductor.
.reduced the total power consumption.
balanced the current demand of the incoming supply.
In a 3-phase 4 wires distribution system, the neutral conductor only carries the
high power factor current
low power factor current.
out-of-frequency current.
out-of-balance current.
The supply to each floor is connected to the rising main by means of
tap-off units
switch-off units
distribution units.
transmission units.
All distribution boards shall be provided with a legible diagram indicated the method used for protection against
fire.
direct contact.
indirect contact.
lightning surge.
Ohm's Law states that the current flowing through a conductor is directly proportional to the potential difference applied across its ends, provided the temperature
is low
is high
remains constant.
is below freezing point.
Ohm's Law states that current is directly proportional to the
voltage (V)
resistance (R)
inductance (L)
reactance (X)
Ohm's states that the current is inversely proportional to
capacitance (C)
resistance (R)
voltage (V).
reactance (X)
A heater takes a current of 10 A from a 230 V supply. What is the resistance?
2.3 Ω
23 Ω
230 Ω
2300 Ω
How much current does a 50 Ω electric iron takes if the applied voltage is 230 volt?
0.22 A
4.6 A
46 A
11500 A
Current flows through the pure inductor is always lags the applied voltage by
45°.
90°.
180°.
270°.
The opposition to the current flow in a pure capacitive circuit is called the
capacitive reactance.
capacitive resistance.
inductive reactance.
inductive resistance.
The function of the service circuit breaker at the intake point is for
leakage protection
earth fault protection
over current protection
over voltage protection
The function of the distribution board is for
lightning protection.
over voltage protection.
energy distribution to final circuits.
energy reduction to power circuits
A person get electric shock contact with live part under normal operation condition is
direct contact.
indirect contact.
normal contact.
shock contact.
