P2 Electricity in the home Flashcards
What are the two types of current?
(d.c.) Direct current is charge pushed around in the same direction by direct p.d. (a.c) Alternating current is one that is constantly changeing direction. P.d. alternating, puches charge arround.
When plotting graphs or traces describe graphs of alternating and direct voltage.
Alternating p.d. varies up and down between positive and negative. ↝↝
Direct p.d. is straight and positive a flat straight line.
What is a circut breaker?
An electromagnet switch that is triggered or tripped by too much current.
In a 3 core cable what is the green/ yellow wire for?
Green /yellow - earth wire
Low resistance wire that connects the applience to earth only used if current escapes onto an applience.
In a 3 core cable what is the blue wire for?
blue - neutral
Current has transfered Electrical energy to applience and is going back with Zero potential.
In a 3 core cable what is the brown wire?
Brown - live wire.
Current carries Electrical energy to the apllience at 230V
In electrical appliences what materials are used for the plug + wire?
3 pin plug UK most cables have 3 wires
Electrical cable - copper and brass because good conductors
Plasitc used beacuse good insulator
: Both are flexible
What is efficiency?
When electrical energy is wasted as heat the device is not very efficient.
Efficiency= the fraction of usefull energy
Name 3 things that can be done to prevent shock from an electric plug?
Earth wire
Double insulation : plastic casing so charge cant escape. no need for earth wire then.
Residual current circut breaker: detect current differemce between live and neutral wires of some current escapes it tripps the the switch.
Explain what an earth wire is .
wire that connects applience to earth, if charge escapes it rushes to earth. current surge will melt the fuse or tip the circut breaker. all appliences with metal cause should be earthed.
Which kind of light source is more efficient?
LED’s are - give off light by a special process no heat = more efficient. Expencive but last longer. small current and waste less so cost less to run.
Fillament Lamps wire high heat resistance = gets hot so glows. lots of energy is wasted in heat.
What is the National Grid?
A network of cables and transformers that transer electrical power from powerstations to consumers.
Explain how electricity gets from power stations to homes.
Powerstations generate/ gather electricity → step up transformers (high p.d. low current less energy wasted) → pylons and transmission lines → step down transformers (decrease p.d. for saftey in homes) → cables connect up homes.
What do step up transformers do and why?
They increase p.d so electricity is sent along cables at high p.d. and low current so less energy is wasted by heating up.
Wat do step down Transformers do and why?
They decrease p.d. before electricity goes into the home for saftey reasons.
