Science 103 Outcomes 7-12 Flashcards
What is overcurrent?
when more current flows than the circuit is designed for
What is a short circuit?
When line and neutral touch, eliminating the resistance of the load
What is the earth fault?
When the line conductor comes in contact with something connected to earth
What is overload?
When too much load is connected to a circuit (where the circuit is otherwise electrically sound)
What is the BS number of a semi-enclosed rewireable fuse?
BS3036
What is a BS3036 semi enclosed rewireable fuse?
one of them old fuses with just a bare wire
What is the breaking capacity of a BS3036 fuse?
1-4kA
What is a cartridge fuse?
an element encased in a ceramic body
What are the BS numbers for the two different types of cartridge fuse?
BS1361 - big
BS1362 - baby
Name two advantages of the BS3036 fuse?
- simple
* can see if it’s blown
Name two disadvantages of the BS3036 fuse
- can easily mix up the size of the wire if replaced
* cable must be downgraded
Name two advantages of the BS1361 fuse
- more accurate than BS3036
* easy to replace
Name two disadvantages of the BS1361 fuse
- can’t see if it’s blown
* more expensive to replace than BS3036
What is a BS1362 fuse ?
a baby ceramic fuse
What colours indicate the different sizes for bs1362 fuses
RED - 3A
BROWN - 13A
BLACK - everything else
What size do BS1362 fuses go up to?
13A
Name two advantages of BS1362 fuses
- the element doesn’t weaken with age
* easy to replace
name two disadvantages of the BS1362 fuse
- can’t see if the fuse has blown
* have to keep a stock of replacements
What is the BS88 fuse?
A more industrial type fuse with metallic end caps
two advantages of BS88
- work very quickly
* no mechanical moving parts
two disadvantages of bs88 fuses
- very expensive to replace
* keeping replacements is costly and takes up space
What the hell does ‘diazed’ and ‘neozed’ refer to?
fuses (bottle neck)
What does H.R.C. mean
High Rupture Capacity
What does H.B.C. mean
High Breaking Capacity
Name four types of fuel
Coal, oil, gas, biofuel
What is the typical output voltage for a power station?
18kV-25kW
Name the three transmission voltages
132kV, 275kV, 400kV
Name the five distribution voltages
66kV, 33kV, 11kV, 400V, 230V
What are the two types of transformer?
core and shell
Why do we need to keep transformers cool?
as the temp increases so does the resistance, causing greater losses
what are the three methods of cooling for transformers?
air, oil, gas
Which two losses occur in the core of a transformer?
- eddy currents
* hysteresis
What is the core of a transformer?
iron
What is the loss that occurs in the winding of a transformer?
heat
What is the winding of a transformer made of?
copper
How do we reduce the losses from eddy currents and hysteresis?
Laminating
In a solar PV panel circuit what increases as more panels are added in series?
the voltage
In a solar PV panel circuit what increases as more panels are added in parallel?
output
Name two advantages of Hydro generation
- eco friendly
* low maintenance
Name two disadvantages of a hydro generation system
- high install cost
* requires flowing water
name two advantages of wind generation
- plentiful energy source
* can store electricity
name two disadvantages of wind energy
- relies on wind
* requires planning permission
Name two advantages of heat pumps
- lowers fuel bills
* fit and forget technology
name two disadvantages of heat pumps
- requires that your house is already well insulated
* high set up costs
What is a Type B RCBO for?
resistive loads i.e. General loads, domestic
What is a Type C RCBO for?
inductive loads i.e. for something with coils/windings like motors or transformers
What are type D RCBOs for?
highly inductive loads e.g. X rays
Name two advantages of a tungsten filament lamp
simple, cheap
Name two disadvantages of a tungsten filament lamp
- only 5% efficient
* fairly short life
Name two advantages of a tungsten halogen lamp
- better colour rendition
* higher efficacy than a filament lamp
Name two disadvantages of a tungsten halogen lamp
- low efficacy
* low lamp life
What are the two types of tungsten halogen lamp?
Linear and capsule
Name two advantages of a high pressure sodium vapour lamp
- excellent lumen maintenance
* long lamp life (24k hrs)
Name two disadvantages of a high pressure sodium vapour lamp
- requires a ballast
* colour rendition is golden white
Name two advantages of a low pressure sodium vapour lamp
- long lamp life
* high efficacy
Name two disadvantages of a low pressure sodium vapour lamp
- poor colour rendering
* expensive to install
Name two advantages of a high pressure Mercury vapour lamp
- more efficient than fluorescents
* intense illumination
Name two disadvantages of a high pressure Mercury vapour lamp
- unflattering bright colour rendition
* requires a warm up period
Name two advantages of an L.E.D.
- saves up to 25x more energy than a traditional incandescent lamp
- long lamp life up to 39k hrs
Name two disadvantages of an L.E.D.
- high upfront cost
* can change colour as a result of age and temperature
Name two advantages of a metal halide lamp
- high efficacy
* life span of 6k-15k hrs
Name a disadvantage of a metal halide lamp
•the life span can be shortened as a result of the oils on your hands if you’re not careful during installation
Briefly describe the operation of a solenoid
- the solenoid has a winding which creates a magnetic field when current passes through it
- an iron rod is placed partly inside
- when the circuit is energised, the rod is pulled into the solenoid fully which should operate the system
Briefly describe the operation of a relay
- in a relay there is a coil which is used to attract a contact to operate a switch
- when the coil has no current thru it, the switch stays open
- then when it is energised, the coil creates a magnetic field which attracts the ferrous contact, closing the switch and completing the circuit.
What is a fault current?
a current which flows through a circuit under fault conditions
What is meant by the term ‘protective conductor current’?
a current that flows thru a protective device
Three advantages of a BSEN60898 circuit breaker
- easy to see when it’s tripped
- can quickly restore the supply
- every breaker is set to manufacturers standard
Three disadvantages of a BSEN60898 circuit breaker
- expensive
- must be regularly tested
- ambient temp can affect performance
Describe the basic operation of an RCD
- An RCD monitors the current going out compared with the one coming in
- if there is an imbalance, a magnetic flux is produced by the toroid which energises the trip coil.
- this opens the double pole switch
What is a cold tail?
The part of the underfloor heating mat or cable which does not heat up because it is the electrical connection.
What are the two types of heat transfer in space heating?
convection and radiation
What is economy 7?
Economy - cheap
7- for 7 hours, between 12-7am
What are the two main types of water heaters?
Stored and instantaneous
What temp should the thermostat of an immersion heater be set to?
55-60 degrees
What stops you from being scalded in an instantaneous water heater?
a scald guard thermostat
Why should water in heaters never get too hot or too cold?
too hot - risk of scalding
too cold - risk of legionella
What is the usual temp for a room thermostat?
20 degrees
What does the programmer do in terms of heating ?
it makes the decision of when the heating will run
What are two valves commonly used in central heating systems? (electrical )
zone valve, three-port valve
What is the unit and symbol for luminous intensity?
candelas, I
What is the unit and symbol for luminous flux
Lumen F
What is the unit and symbol for illuminance
lux E
What is colour rendering
a lamps ability to show colours as they truly are
How is a lamps efficiency measured?
in lumen watts
What does GLS mean?
General Lighting Service
