問題一覧
1
In a three phase, four wire system the neutral conductor is needed to ?
provide for single phase supplies
2
A current flowing towards the viewer in a cross- section of a conductor is shown in a diagram by
a dot
3
The B type MCB will operate magnetically at
3-5 times it rated current
4
Where trunking passes through a wall or ceiling it must contain ?
a fire barrier
5
IS/EN 60309 socket outlets greater than 16 amps shall be supplied by?
seperate circuit
6
The initials IP mean
ingress protection
7
In electromagnetic induction the direction of magnetic field, current flow and the force on a conductor are determined by?
flemings left hand rule
8
When using a clip on ammeter to check the motor current, it is necessary to have the motor
connected to the supply and running
9
Extra low voltage cables may be run in a steel trunking system along with the low voltage cables
all cables are insulated for the highest voltage present
10
What is the formula for calculating capacitance of two capacitors connected in parallel?
Ct= c1+c2
11
From lenz law, when the current in a coil increases the self induced voltage will
produce a current in opposition to the increasing current
12
If the primary voltage of a transformer is greater than its secondary voltage it is called a ?
step down transformer
13
The type of rotor used in a three phase induction motor is ?
a squirrel cage rotor
14
One advantage of steel conduit over plastic conduit is ?
a separate protective conductor is not required
15
Which of the following is the abbreviation used to indicate the current rating of a circuit fuse or MCB ?
In
16
The cable gland used in terminating a SWA cable
clamps the armouring wires securely
17
A polarised capacitor should never be used
in an AC circuit
18
Where the lengths of steel trunking are joined, they must be
bonded tiger with copper straps
19
The two windings in a transformer are called the
primary and secondary
20
IS/EN 60309 plugs and sockets outlets rated for 400 are what color
red
21
The start button is a direct on line (D.O.L) control circuit is wired in ?
series with the coil
22
Voltage drop in cables can be reduced by ?
increasing the cross sectional area of the conductors
23
When using flemings right hand or left hand rule the second finger points in the direction of
current flow
24
An AC supply has a frequency of 200Hz. This means that
the waveform completes 200 cycles every second
25
The diagram of one full sinusoïdal waveform includes
both positive and negative half cycles
26
The minimum level of IP protection on all fittings where water hosing is used in a farm location is ?
IP 55
27
The gas normally used to fill an incandescent lamp is ?
argon or nitrogen
28
Which of the following illustrates stroboscopic effect
rotating machinery appears stationary
29
Once a single phase capacitor start motor is running at its rated speed the centrifugal switch
disconnects the start winding from the supply
30
The highest value reached by an alternating voltage in a half cycle is called
maximum of peak value
31
If an iron core is inserted in a solenoid and the current is maintained at a constant value the magnetic flux will
increase in strength
32
The conductors contained in busvar trunking are usually
bare copper or aluminum bars
33
A running coupler is used on steel conduit
when neither conduit can be rotated
34
Single phase 230 ac supplies are taken from a
400v three phase four wires system
35
A capacitor consists of two
conducting materials separated by an insulator
36
Plastic conduit must be used only within the manufacturers prescribed ranges of
ambient temperature
37
Standard supply of voltage in Ireland
400-230
38
Metallic cable tray is
an exposed conductive part and must be earthed
39
The stop button in a direct on Line DOL control circuit is wired in
series with the start button
40
If two phases of the supply to a three phase motor are reversed
the motor will rotate in the opposite direction
41
Extra low voltage cables may be run through a steel trunking system along with low voltage cables provided that
they are run in seperate compartments within the trunking
42
In a permanent magnet, the lines of flux external to the magnet are said to start
at the magnetic North Pole
43
An example of a device that works on the principle of electromagnetism is a
relay
44
The farad is the unit of
capacitance
45
A transformer works on the principle of
electro magnetic induction
46
Eddy currents losses in a power transformer is minimized by
constructing the core with laminated layers
47
The main reason for limiting the number of cables which may be run through a conduit is
that cables may be easily drawn in and removed
48
The main advantage of installing steel conduit over pvc conduit is that
it provides superior mechanical protection to pvc
49
Good earth continuity on a steel conduit installation requires
low resistance
50
Conduit boxes are galvanised to
prevent corrosion
51
If discrimination between fuses is correct in an electrical installation then
the fuse nearest a fault will rupture first
52
The color of the first phase of a three phase and neutral fixed wiring system must be
brown
53
A large office having a three phase four wire supply derives its 230v supplies from
any one phase and neutral
54
Full on and off control of the lighting in a corridor from three positions requires which of the following combination of switches
two 2 way and one intermediate types
55
The resistivity (specific resistance) of a conductor depends on its
material composition
56
The tables of current ratings and voltage drop in cables in the ETCI rules are based on an ambient temperature of
30°
57
The main reason for removing a section of the outer sheath of an SWA cable prior to terminating the gland is to ensure that the
armour conductors are clamped within the gland body
58
The surface finish of a cable tray used in damp situations must be
hot dipped galvanized
59
A three phase induction motor has the characteristics of
constant speed about 5% below synchronous speed
60
All motors convert to
electrical energy to mechanical energy
61
A remote stop button connected to a direct on line started should be
connected in series with the local stop button
62
If an insulated cable is wound so that it forms many circular loops or coils it is called
solenoid
63
If a soft iron core is inserted into a solenoid the magnetic field will
become more concentrated
64
Any circuit that induces EMF into itself is said to be
self inductive
65
Two coils are placed side by side one induces an EMF into the other the result is called
dynamic induction
66
The Henry is the unit of
inductance
67
If the north seeking poles of two magnets are brought close together they will
repel each other
68
A material that can be magnetized is said to be
ferromagnetic
69
A permanent magnet may lose its magnetism if it is
heated or hammered
70
The construction of a capacitor is accurately described as
having two conducting plates separated by an insulator
71
Which of the following statements is correct
exceeding the rated voltage of a capacitor will damage it
72
Convert micro farad to farads
0.00025
73
The material between the plates of a capacitor is known as
the dielectric
74
Which is the standard frequency used in this country
50hz
75
The hearing effect of 25 amps AC when measured with a multimeter compared 25 amps DC is
the same
76
Which of the following characteristics applies to AC but not to DC
frequency
77
The effect that limits the flow of current in an AC circuit containing a capacitor is called
capacitance reactance
78
Which of the following statements is true
the transformer works on the principle of mutual induction
79
A class 1 transformer has
it’s metal core connected to earth
80
Which of the following is the principle in which the transformer works
all of those listed
81
PVC conduit is suitable for use within the temperature ranges of
-5 and 65 degrees
82
The primary function of metallic cable tray is to
provide support and fixing for sheathed cables
83
One disadvantage of PVC conduit
it expands 5 times more than steel conduit
84
Under floor trunking or ducting may be used for
all types of circuits where properly segregated
85
Multiple surface runs of armoured cables are normally installed
on cable tray
86
The phase voltage in this country is
230 v
87
Power stations that are connected to the grid system
generate the same supply frequency
88
In large commercial installations discharge lighting circuits are divided over three phases to overcome the
stroboscopic effect
89
Minimum IP rating for industrial sockets on agricultural and horticultural environments is
IP 44
90
The purpose of the main switch at the supply intake position is to
provide isolation
91
Tungsten halogen lamps are also known as TH lamps. What is their life expectancy of these lamps
3,000 to 5,000 hrs approx
92
A tungsten halogen lamp that is operated at slightly more than its rated voltage will have a
shorter life and brighter light
93
The fluorescent fitting has a capacitor connected between live and neutral at the beginning of the fitting circuit that helps to
improve the power factor of the unit
94
The letters CFL translate as follows
compact fluorescent lamps
95
Voltage drop in cables can be reduced by
increasing the CSA of the conductors
96
When using SWA cable the steel wire
must be glandes and connected to the protective conductor
97
SWA cable is suitable for use
in underground electrical supplies
98
Electrolytic action occurs when
copper is in contact with aluminum
99
Formula for the calculation of the volt drop in cable is
millivolt per amp per meter
100
Another name for an auxiliary winding in a single phase motor is
the start winding