June 2022

Question 1

List three technical specifications relating to the selection of a wall mounted light
switch when recording on a materials list.

Answer 1

Gangs or number of switches incorporated
Ways or switching operation
Function
Finish or colour or materia

Question 2

State the two types of losses associated with a transformer core.

Answer 2

Iron
Copper

Question 3

State two types of single-phase AC motor.

Answer 3

Capacitor start
Split phase
Universal
Induction

Question 4

State two types of fuse commonly found in electrical installations protecting circuits.

Answer 4

HRC or HBC
Cartridge
Semi-enclosed or rewireable
Plug fuse

Question 5

List three protective conductors commonly installed in electrical installations as given
in BS 7671.

Answer 5

Earthing conductor
Main protective bonding conductor
cpc
Supplementary equipotential bonding conductor

Question 6

List the first three tests carried out on a newly installed radial lighting circuit.

Answer 6

Continuity (or continuity of conductors)
Insulation resistance
Polarity

Question 7

List three documents that would assist in fault diagnosis which are to be kept by the
client.

Answer 7

Electrical installation certificates
Periodic reports or electrical installation condition reports
Operation manuals or manufacturers data
Fault reports

Question 8

List three factors that affect the decision between repairing or replacing a faulty item
of equipment.

Answer 8

Cost
Availability
Downtime
Legal responsibility

Question 9

State the two methods of providing Basic Protection within a dwelling in accordance
with BS 7671.

Answer 9

Insulation
Barriers or enclosures
SELV

Question 10

List three labels, as given in BS 7671, that would be located on the installation
consumer unit at the origin of an electrical installation.

Answer 10

Periodic test notice
RCD test notice
Alternative supplies
Voltage label
Mixed wiring colours

Question 11

Explain the difference between an earth fault and a short circuit including if circuit
breakers or RCDs operate under each condition.

Answer 11

Earth fault is low impedance path between live (or line) and earth
Short is low impedance path between live conductors
If impedance between line and earth is low enough, circuit breaker will operate for both
RCDs will not detect short circuits

Question 12

A continuity of ring-final circuit test is being undertaken during an initial verification.
During step 1, the following measurements were made
 r1 – 0.8 Ω
 rn – 0.8 Ω
 r2 – 1.34 Ω
Explain the relationship between these results and the expected results when line
and neutral are cross connected and tested at each socket-outlet.

Answer 12

The results indicate a reduced size cpc in the circuit and Line and N are the same csa (1 for some
of this relationship).

0.8 + 0.8
4
(1) = 0.4 Ω (1)

Question 13

Explain why the earthing conductor must be disconnected from the installation main
earthing terminal whilst undertaking a test to obtain a value of Ze.

Answer 13

remove parallel paths
through other services or metallic parts (answer must indicate a path)
ensure only electrical earth is providing low impedance