P2.4 Flashcards
Mains electricity is…..
Useful but can be very dangerous
What do electrical appliances transfer
Energy
What is the power of an electrical appliance
The rate at which it transforms energy
What do most appliances have printed on them
Their power and their potential difference
From the power and the potential difference of an appliance what can we calculate
Their current and the fuse they need
What type of current always passes in one direction
Direct current
What type of current is supplied by cells and batteries
Direct current
What is an alternating current
One that is always changing direction
What type of current is the mains electricity
An alternating current
What frequency is the mains electricity
50 hertz
What is the potential difference of the uk mains electricity
230v
What are most mains electricity appliances connected to
The mains using cable and three pin plugs
What does it mean if an electrical fault causes too great a current
The circuit is disconnected by a fuse or circuit breaker in the live wire
What happens when the current in a fuse wire exceeds the rating of the fuse
It will melt and breaks the circuit
What are some circuits protected by
Residual current circuit breakers (RCCBs)
How do residual current circuit breakers operate
By detecting a difference in the current between the live and neutral wires
What operates much faster than a fuse
Residual current circuit breakers
What are usually earthed
Appliances with metal cases
Why do some appliances have no earth connection
Because they are double insulated
What protects the wiring of the wireof the circuit
The earth wire and fuse together
When does a resistor get hot
An electrical charge flows through it
What is a lot of energy wasted as in a filament lamp
As heat
What wastes less energy than a filament bulb
Power saving lamps such as compact fluorescent lamps
What can be shown on an oscilloscope screen
Electricity appliances
What is a cathode ray oscillope
Voltmeter
What happens when u plug a dc supply on a cathode ray oscillope
Straight line
Likely electrical hazards f
Long cables
Water near sockets
Too many plugs into one socket
What are three wires in a plug
Neutral wire
Live wire
Earth wire
How does an earth wire work
It is attached to the metal casing of the appliance and carries the electricity to earth and away from u
The more current that flows ….
The more heat produced
What does a bigger voltage mean
More heating because it pushes more current through
How do filament work
They pass a current through a thin wire, heating it up so much that it glows
