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What is the function of a battery?
Change chemical energy to electrical energy .
Function of the power supply
Provides electrical energy
Function of the bulb
Changes electrical energy to light and heat energy .
Function of the switch
Makes or breaks circuit
Function of the resistor
Restricts current. Changes electrical energy into heat energy .
Function of a variable resistor
The resistance can be changed and controls current flow .
Function of ammeter
Measures current .
Function of voltmeter
Measures voltage.
function of a diode
Lot of resistance one way .
Function of fuse
Breaks circit when current is too great .
What is the formular for finding the total resistance of resistors in a parallel circuit?
1/R(T)= 1/R(1) + 1/R(2) + R/(3)
Why are houses wired in parallel circuits ?
*You can add socket anywhere
*Every socket gets 230volts
*Appliences can be put on and off independently
How many watts in mega watt ?
1,000,000
If the current decreases , what happens to resistance ?
It increases
Advantages of mcb to fuse .
*Quicker
*More sensitive
Advantages and disadvantages of coal
Advantages
*creates jobs
*reliable
Disadvantages
*Releases CO2
*Releases SO4
Advantages and disadvantage of Nuclear energy .
Advantages
*No CO2 Released
Disadvantages
*Waste produced is ionising
*waste doesn’t decompose for thousands of years
Advantages and disadvantages of wind energy .
Advantages
*No CO2 released
*renewable
Disadvantages
*not effective all the time (unreliable)
*Can ruin skylines-eye sore
Advantages and disadvantages of hydroelectric energy.
Advantages
*Produces energy fast(?)
*Renewable
*Creates jobs
Disadvantages
*needs a lot of water and land
function of step up transformer
Increase voltage to decrease energy loss
step-down transformer
a transformer that decreases voltage because it's safer
How efficient can transformers be ?
Up to 99%
Describe the national grid system .
The national grid system is a network of linked cables connecting users to power station.
Why are metals good conductors?
They have free electrons .
The electrons start to vibrate and pass energy on to the next atom and vibrate etc.
What is the process of convection (think of water boiling)
*As the air heats up it increases in volume (decreases in density) and rises .
*Once it rises it begins to cool and decrease in volume (increasing in density )
And the process continues.
Why does a cavity wall reduce heat loss by covection ?
Insulaton contains trapped air , air is a poor conductor thus reducing convection .
Heat is transferred directly to a person sitting in front of a fire by ...
Radiation
What is conduction?
Heat traveling through solids
*The atoms vibrate and pass energy to the next atoms
*Free electrons colide with the positive ions in the metals
How to stop conduction
Use air - air is a poor conductor.
Why are metals good conductors?
They have free electorons .
What is convection?
Air or water particles becoming less dense and rising . Then becoming more dense and falling .
How to stop convection
Use air - air is a poor conductor
What colours are the best and worst absorbers and emmiters ?
Best is black
Worst is silver/white
What does a a DC current graph look like ?
Straight flat line
What is DC current?
Current that goes in one direction . dtays the same value .
What kind of current is available from sockets in home and school ?
AC
What is AC current?
Current that changes from + to - . It also changes value .
What does a AC graph looks like ?
Line that curves upwards and downwards like a wave
What is the name of the wire on the left of a plug ?
Neutral wire
What is the wire that's on the far right of the plug ?
Live wires
What us the wire at the top of the plug ?
Earth wire
function of the live wire?
*The live wire carries current to device. Same Current as neutral
Function of the Neutral Wire?
*neutral wire completes circuit same current as live.
Function of Earth Wire?
*Connected to metal case, transfers current away from device to the ground, to prevent live wire overloading
Features of a Ring Main
*less current in each wire
*can install new sockets
*every socket recieves 230 volts
What is the funtion of an MCB
Breaks circuit when the current is too much .
Note 
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