March 22 Flashcards
List three things that need to be checked regarding the materials, given on
a material schedule, before they are obtained and installed.
the right type
fit for purpose
in the correct quantity
suitable for work to be completed cost efficiently
List three methods of generating electricity using renewable energy.
Solar
Wind
CHP
Tidal
Hydro (but not pumped storage)
Explain one reason why AC is used in preference to DC for most electrical
distribution in the UK.
AC voltage can easily be stepped up and down (1) using transformers (1) to
minimise losses and voltage drop (1).
List three types of AC motor controller.
direct-on-line
star-delta
rotor-resistance
soft-start
variable frequency
other suitable
Explain why electric immersion heaters in hot water cylinders must have a
thermal cut-out within.
The thermal cut-out acts to prevent the cylinder overheating (1) and dangerously
pressurising (1) in the event that the thermostat fails (1).
List three different devices that can provide overcurrent protection.
Fuse, circuit breaker, thermal overload trip
Explain why an IT earthing arrangement may be selected for an installation.
Where unexpected (1) disconnection (1) of a circuit could cause danger (1)
Explain why three-phase motor circuits do not usually include a neutral
conductor.
Because all three phases are balanced (1), there will be no neutral current (1), and thus
a conductor is not required (1).
List, in the correct order, the first three tests to be performed during the
initial verification of a new radial final circuit in accordance with BS 7671.
Continuity (of protective conductors) (1)
Insulation resistance (1)
Polarity (1)
Explain, giving an example, how the sense of touch could be used during an
inspection of a metallic conduit system.
The sense of touch may be used to check the conduit (1) is securely fastened to the
wall (1) by trying to move it (1).
Explain what is verified during the functional test of a passive infra-red
movement detector controlling a number of outdoor luminaires.
Switches the correct luminaires (lights) (1)
Senses movement in the right places (1)
Operates at the correct light level (1)
State three GS38 requirements for an approved voltage indicator used to
safely isolate a circuit prior to fault diagnosis.
Fused leads
Exposed tips no longer than 4mm (or 2mm)
Flexible and robust leads
Identifiable leads (accept colour coded)
State two sources for safety services as given in BS 7671.
Storage batteries
Primary cells
Generators
Separate feeder
State the minimum degree of IP protection for each zone in a location
containing a bath.
Zone 2 – IPX4
Zone 1 – IPX4
Zone 0 – IPX7
Explain where, within an installation, surge protective devices may be
required.
Surge protective devised may be required at the origin (1) of the installation, any sub
distribution boards (1) and at socket-outlets or equipment terminals (either - 1).
