Electricity (10) Flashcards
How many wires are there in a plug
3
What are the names of the wires in a plug
Live wire
Neutral wire
Earth wire
The plug could still work without which wire
The earth wire
What does the live wire do
Carries the voltage
What does the neutral wire do
Completes the circuit
What does the earth wire do
Prevents accidents. Safety wire
If an appliance has a plastic casing and no metal parts showing then it said to be ____________ insulated
Double
Plastic is an __________ so it stops current flowing
Insulator
Where might an appliance not need an earth wire
If it is double insulated
All appliances with metal cases must be ___________ to reduce the danger of electric shock
Earthed
What does earthing mean
The case must be attached to an earth wire
An earthed conductor can never become ___________
Live
Name 3 safety precautions you may take when using plugs
Check live parts aren’t exposed
Check the cable isn’t frayed
Check there’s no water near by
Never push a metal object into a plug socket
If a fault develops in which the live somehow touches then metal case, the because the case is earthed, a big ___________ flows in through the live wire, through the case and out down the __________ wire. This surge in current blows (melts) the ________ which cuts off the live supply meaning it is impossible to get an electric shock
Current
Earth
Fuse
How do circuit breakers work
When they detect a surge in current in a circuit, they break the circuit by opening a switch
What is normally the voltage of the live wire
230V
What is voltage
The difference in charge between 2 points
Basically the driving force that pushes the current round
What is current
The rate at which charge is flowing
What is another term for voltage
Potential difference
What is the voltage of the the neutral wire
0V
Circuit breakers operate __________ than a switch
Faster
Why are fuses slower than circuit breakers
Because you have to wait for the current to melt the fuse
Normally exactly the same current flows through the ________ and ___________ wires. If you touch the live wire then a small but deadly ___________ will run through you to the _________. This means the neutral wire carries ________ current than the live wire. The circuit breaker detect this difference in current and quickly cut off the power by opening a __________
Live and neutral wires. Current Earth Less Switch
When there is an electric current in a resistor there is an energy transfer which ________ the resistor
Heats
The heating effect increases a resistors _____________ so _________ current will flow, or a ____________voltage will be needed to produce the same current
Resistance
Less
Greater
Name an advantage of the heating effect on a circuit
If you want to heat something e.g. toaster, kettle
What is electrical power
The rate at which an appliance transfers energy
An appliance with a _______ power rating transfers a lot of energy in a short time
High
An appliance with a high power rating will draw a __________ current from the supply
Large
What is power measured in
Watts
What is the formula for electric power
P = IV
Fuses should be rated as near as possible but just slightly __________ than the normal operating current
Higher
What is the formula for energy transferred
Current x voltage x time
What is resistance
Anything in the circuit that slows the flow down
The relative sizes of the voltage and resistance decide how big the __________ will be
Current
If you increase the voltage - then _________ current will flow
More
If you increase the resistance - then _________ current will flow
Less
An ammeter measures _________ in _____
Current in amps
Where must an ammeter be placed in a circuit
In series
A voltmeter measures _________ in ______
Voltage in volts
Where must a voltmeter be placed in a circuit
Parallel around the component under test
In the standard test circuit, it doesn’t matter where the components in __________ are
Series
In __________ circuits, the different components are connected in a line
Series
In ____________ circuits, each component is separately connected to the +ve and -ve of the supply
Parallel
In ___________ circuits, you cannot control which components current flows through it either flows through all the components or none of them
Series
In _____________ circuits, disconnecting a component will hardly affect the others
Parallel
When drawing a ____________ circuit diagram, all the components will be one after the other along the wire
Series
When drawing a ___________ circuit diagram, each component is on its own loop circuit. To add a component, just add another loop to the diagram
Parallel
In __________ circuits, removing or disconnecting one component will break the circuit, stopping all the other components
Series
Use of series circuits
Not very useful
Some christmas lights
Use of parallel circuits
Household electrics
_____________ are always connected in parallel with a component even in a series circuit
Voltmeters
_____________ are always connected in series even in a parallel circuit
Ammeters
In _____________ circuits the same current flows through all parts of the circuit. i.e. A1=A2. The size of the current is determined by the total __________ of the cell(s) and the total _______________ of the circuit
Series
Voltage
Resistance
The total resistance of the circuit depends on the number of ________________ and the type of ________________ used.
Components
Component
More components = more _____________
Resistance
Charge can be positive or negative - and when charge flows it is called ____________
Current
In solid metal conductors (e.g. copper wire), charge is carried by _______________ charged electrons
Negatively
When current flows past a point in a circuit for a length of time, then the charge that passed is given by this formula:
Charge = Current x Time Q = I x T
More charge passes around a circuit when a ___________ current flows
Bigger
Charge is measured in __________
Coulombs
