GCSE WJEC ~Physics ~ unit 1 (copy)

What is the function of a battery?

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 .