[PS5PY]
Books are are written by ex-examiners and [ANONYMIZATION] have a spec have several specimen answers . They have here is an answer is too [UNCLEAR] in an exam . This one 's excellent because these are the [UNCLEAR] .
WMN: K7F_372
Dialogue: K7F
[PS5R0]
Alright yeah .
[PS5PY]
This one erm he sort of tried hard and put a lot in , thinks he should get full marks but he 's not going to get very much because he 's missed this , he 's not answering that properly
[PS5R0]
Yeah .
[PS5PY]
and he said that . But it 's very good to see where people go wrong and to er help you get it right , and that one is the one [UNCLEAR] . Is it like that in this one ?
[PS5R0]
What 's that ? My
[PS5PY]
Ah [UNCLEAR] [ANONYMIZATION] , are showing how people answer different , how they got
[PS5R0]
Erm yes er yeah .
[PS5PY]
How [UNCLEAR] marks . And right , electricity . Okay what 's erm the difference between a metal and a non-metal ?
[PS5R0]
Erm metal and non-metal . Erm a non-metal is a metal 's a solid no ?
[PS5PY]
Most metals are solid . Erm can you think of a one metal which is n't a solid at normal temperatures ?
[PS5R0]
No .
[PS5PY]
Find it you might find it in a thermometer .
[PS5R0]
Mercury .
[PS5PY]
Right .
[PS5R0]
Right .
[PS5PY]
So [UNCLEAR] solid [UNCLEAR] non-metals [UNCLEAR] . Some of them are solid some of them are n't . Er physical properties of metals . What will metals do ? What can metals do very well that non-metals ca n't do ?
[PS5R0]
Erm well they 're hard so they can erm make things . Because they 're
[PS5PY]
You can make things . Right
[PS5R0]
s
[PS5PY]
you can make things with them
[PS5R0]
solids .
[PS5PY]
Good . They 're hard you can make things out of them . Erm a lot of them are shiny . How do you make erm how do you make wire ?
[PS5R0]
With metal .
[PS5PY]
Okay . How do you make it with the metal ? What do you do with the metal to make wire out of it ?
[PS5R0]
Heat it melt it .
[PS5PY]
You do n't need to heat it they just there 's a bar of it and they pull it .
[PS5R0]
Oh right yeah .
[PS5PY]
Pull it through a tiny hole . [UNCLEAR] stick it through a dye .
[PS5R0]
Mm .
[PS5PY]
So it 's if you can pull it out it 's ductile .
[PS5R0]
Mm .
[PS5PY]
Have you ever tried hammering any metals ?
[PS5R0]
No .
[PS5PY]
Lead or soft metals you can hammer them into shape . Seen anyone beating a car panel it 's got
[PS5R0]
Yeah .
[PS5PY]
a dent and they 're beating it [UNCLEAR]
[PS5R0]
Yeah .
[PS5PY]
so they 're malleable . You can hammer them into shape .
[PS5R0]
Right .
[PS5PY]
They 're ductile malleable do n't need the proper words you just say they can be pulled out . If you try that with erm a piece of wood , you try to pull it out into a long thin wire it would just break . Try it
[PS5R0]
Yeah .
[PS5PY]
with a piece of china or something like that it 'll just break .
[PS5R0]
Right .
[PS5PY]
All metals will stretch out , it 'll get thinner [UNCLEAR] ductile . Malleable you can batter it
[PS5R0]
Right .
[PS5PY]
into shape . So those are the some of the physical properties . Have fairly high melting points . Some of them not as high as the non-metals but most of have got to get to a few hundred degrees C before they start [UNCLEAR] . Erm some of the uses of metals . Tell me some .
[PS5R0]
Oh erm , the uses of metals . What actually what erm oh god
[PS5PY]
What could you use metals for ?
[PS5R0]
Er anything computers
[PS5PY]
Right right . So you can use them for because of because of it 's cos you can draw it out you can make wires out of it . You can shape it into almost anything . You can make very specially shaped [UNCLEAR] for
[PS5R0]
Yeah .
[PS5PY]
almost anything . But there 's another another use of metals erm two sticks about say about [UNCLEAR] one 's made of wood and one 's made of copper . Erm someone 's going to heat one end and then hold the other end . Which one would you rather hold ?
[PS5R0]
Copper .
[PS5PY]
Wood .
[PS5R0]
Oh !
[PS5PY]
We 'll try it .
[PS5R0]
No the wood one .
[PS5PY]
Why ?
[PS5R0]
Because wood takes longer to burn , copper would just you would you could you would feel the heat you had if
[PS5PY]
Right .
[PS5R0]
you held the the end .
[PS5PY]
The wood would be the first to burn but you would n't feel much . Would n't feel anything
[PS5R0]
No .
[PS5PY]
holding the end of the wood . But holding the copper after a few seconds the heat all the heat 'd be transmitted through
[PS5R0]
Yeah .
[PS5PY]
to your hands . Conducted it .
[PS5R0]
Mm .
[PS5PY]
So metals are ?
[PS5R0]
Conductors .
[PS5PY]
Good conductors of ?
[PS5R0]
[PS5PY]
Go on . Good conductors of what ?
[PS5R0]
Good conductors of
[PS5PY]
Well what 's it just been conducting ?
[PS5R0]
Electricity .
[PS5PY]
Good , that 's another one . Good conductors of heat .
[PS5R0]
Heat yeah .
[PS5PY]
And good conductors of electricity .
[PS5R0]
Mm .
[PS5PY]
Or we sometimes just say , good conductors . So what about the insulators the non-conductors ? Can you think of any of those ? Materials which are very good at stopping electricity , stopping heat getting through . If if a material conducts electricity well , it conducts heat well because it 's very there there there they work on the same process . If it 's an insulator it stops heat getting through and it 'll stop electricity getting through as well .
[PS5R0]
Mm .
[PS5PY]
So can you think of any good insulators ?
[PS5R0]
Erm erm [UNCLEAR]
[PS5PY]
Oh oh yes .
[PS5R0]
Erm
[PS5PY]
Erm have you got an ironing board ?
[PS5R0]
Yeah .
[PS5PY]
Got to put the iron down on apart from . [UNCLEAR]
[PS5R0]
On plastic .
[PS5PY]
So there 's a special little bit that you put the iron down on .
[PS5R0]
Oh metal .
[PS5PY]
Is it metal ?
[PS5R0]
I du n no [UNCLEAR]
[PS5PY]
Erm sometimes it 's asbestos .
[PS5R0]
Right .
[PS5PY]
Er the plug and the cable going to any electrical appliance .
[PS5R0]
Mm .
[PS5PY]
Erm how does it conduct electricity ? What 's what 's insi what 's inside that wire that conducts electricity ?
[PS5R0]
A fuse .
[PS5PY]
No , that what 's the wire made of inside ?
[PS5R0]
Erm no it 's not zinc is it ? Copper ?
[PS5PY]
Okay good copper . It 's a metal . Inside there 's a metal , but it 's not just two bare wires is it ?
[PS5R0]
No .
[PS5PY]
So what 's wrapped round the bare wires ?
[PS5R0]
Erm protector so it wo n't it does n't erm it slows it down . Does it slow it down ? Cos if you had just if you did n't have the thing erm over the wire it would just burn right through very quickly .
[PS5PY]
So is it you 've seen you 've wired a plug have n't you ?
[PS5R0]
Yeah .
[PS5PY]
Well [UNCLEAR]
[PS5R0]
You 've always got something covering the wire have n't you ?
[PS5PY]
Got something covering the wire . What is it ?
[PS5R0]
Plastic .
[PS5PY]
Right . So the plastic is there because it 's a good insulator .
[PS5R0]
Yeah .
[PS5PY]
If you covered the wire with more metal say you put two pieces of wire spare wire
[PS5R0]
Mm .
[PS5PY]
or wrap some aluminium foil round these to protect them , not going to be much good .
[PS5R0]
No .
[PS5PY]
Aluminium 's a good conductor .
[PS5R0]
Yeah .
[PS5PY]
Very good conductor . Erm so plastic is an insulator .
[PS5R0]
Mm .
[PS5PY]
Glass ceramic most of the non-metals are good insulators . Somewhere in be in between are a very interesting group called semiconductors . Have you heard of those ?
[PS5R0]
I have yeah .
[PS5PY]
Yep and they 're probably nowadays as more important than the conductors . And that 's what we use for electronic circuits . So semiconductors are things that sort of conduct and sort of do n't .
[PS5R0]
Yeah .
[PS5PY]
Erm
[PS5R0]
In between .
[PS5PY]
they just need a little push to make them go one way or the other so
[PS5R0]
Mm .
[PS5PY]
because of that we can control , we can say turn on turn off whether they let the electricity go through or not . Erm so semiconductors Erm tell me about an electrical circuit , how it works .
[PS5R0]
Well you have if you 're doing an electric circuit you 've got to have a er a bulb and a switch .
[PS5PY]
Mm .
[PS5R0]
And batteries to g to do the circuit and you can have erm volts in it as well .
[PS5PY]
Okay what are what are volts ?
[PS5R0]
Volts erm it 's a term used for electricity ,
[PS5PY]
Okay .
[PS5R0]
volts .
[PS5PY]
Right , what sort of electricity ?
[PS5R0]
Currents . The current of the electricity .
[PS5R0]
Good . Does n't have to be current but it usually is . Best thing to do is to draw a little picture erm so what does volts measure ?
[PS5R0]
The amount of electricity that 's going
[PS5PY]
Yeah . It measure the the potential , erm I 've got a three volt battery in there , somewhere cos I 'm working [UNCLEAR]
[PS5R0]
[PS5PY]
I 'm going to make you hold one end sort of there 's the there 's the battery , going to make you put one finger on one terminal the other finger your other hand on the other one .
[PS5R0]
Mm .
[PS5PY]
One and half volts . Is that going to kill you ?
[PS5R0]
No .
[PS5PY]
No . Erm drive it with erm a hundred and thirty two thousand volts ?
[PS5R0]
Yes .
[PS5PY]
Okay .
[PS5R0]
The high voltage
[PS5PY]
Why ? What 's what 's the difference then ?
[PS5R0]
Well it 's got a higher voltage .
[PS5PY]
Yeah what 's what does that mean ? Why is that
[PS5R0]
It 's
[PS5PY]
going to be ?
[PS5R0]
Well it 's higher on electricity it 'll give me an electric shock .
[PS5PY]
Mhm . How does it do it ?
[PS5R0]
It goes through your nervous system .
[PS5PY]
Okay .
[PS5R0]
Into you 're arteries
[PS5PY]
Right
[PS5R0]
and your heart .
[PS5PY]
Right . So it 'll go through you and it 'll paralyze your muscles , so you stop breathing and your heart stops .
[PS5R0]
Mm .
[PS5PY]
And effectively , it 's a bit like drowning .
[PS5R0]
Mm .
[PS5PY]
Erm [UNCLEAR] get your heart started again . So that 's another good point erm you know what to do if someone 's had an electric shock ?
[PS5R0]
Do n't touch them .
[PS5PY]
Right .
[PS5R0]
Cos they 'll still have electricity
[PS5PY]
Okay .
[PS5R0]
on them .
[PS5PY]
You do n't touch them , what do you do ? [UNCLEAR]
[PS5R0]
Turn off all the mains .
[PS5PY]
Good .
[PS5R0]
Erm get a stick or something
[PS5PY]
Right . Something like a wooden
[PS5R0]
Wood .
[PS5PY]
stick or
[PS5R0]
Yeah .
[PS5PY]
a rope [UNCLEAR] rope and loop him round .
[PS5R0]
Drag him away from the actual
[PS5PY]
Right .
[PS5R0]
mains [UNCLEAR]
[PS5PY]
Okay . And then what do you do ? When you 've got them away from the mains , what d' ya do with them ?
[PS5R0]
Erm god I 've done a first aid course . Erm what do you do ? Right erm . Could you still touch them if you 've pulled them away from the mains and everything ?
[PS5PY]
Yeah . Once you 're sure you 've pulled them away . But as you say , switch off first and then still use a stick or something to get them away because it maybe the switch does n't work and maybe that 's why they 've been electrocuted in the first place . Cos they thought it was switched off
[PS5R0]
Yeah .
[PS5PY]
and it was n't . So get them away from the mains and then what do you do ?
[PS5R0]
Erm do the quick A B C.
[PS5PY]
Right , good and erm
[PS5R0]
Check the airway , check the breathing , check
[PS5PY]
Yeah .
[PS5R0]
the circulation .
[PS5PY]
And just treat it as a [UNCLEAR]
[PS5R0]
Yeah .
[PS5PY]
Erm
[PS5R0]
Just try and get their heart beat started .
[PS5PY]
Get them breathing started because the the longest they 've been paralysed er
[PS5R0]
Try and get some oxygen in there .
[PS5PY]
Get that going and [UNCLEAR] ring for an ambulance .
[PS5R0]
Yeah .
[PS5PY]
Erm so what 's volts all about ? Well it takes a while to explain , but I 'll try and do it quickly . Erm let's see This is a reservoir of water , right ?
[PS5R0]
Mm
[PS5PY]
Erm if the water 's very high and say we have a little a little pipe coming through there in the bottom .
[PS5R0]
What 's that ?
[PS5PY]
That 's the dam .
[PS5R0]
Oh right , yeah .
[PS5PY]
[UNCLEAR]
[PS5R0]
[PS5PY]
So that 's the that 's the wall and this is the water .
[PS5R0]
Right .
[PS5PY]
Now if the water 's fai water level is fairly low , there 'll just be a little trickle coming out here .
[PS5R0]
Mm .
[PS5PY]
If there 's a lot of water in the dam , right up there , just pull the plug out here it 's going to really shoot out .
[PS5R0]
Yeah .
[PS5PY]
Be a lot of pressure there because there 's a lot of height
[PS5R0]
Mm .
[PS5PY]
of water . Well you can think of the height of the water as like a voltage .
[PS5R0]
Mm .
[PS5PY]
It tells you ho it 's called potential volts , measures potential . It measures electrical potential , you can just call it potential . And if you think of what potential it 's got erm sort of like this squirt , if you like . If you [UNCLEAR]
[PS5R0]
Mm .
[PS5PY]
Now if we have a little hole in there , we 'll only get a little bit of water coming out , no matter what sort of
[PS5R0]
[UNCLEAR] pressure is n't it ?
[PS5PY]
Well let's say let's say we 've got a fixed pressure now , we 're not going to mess about with the height of the water , it 's a constant hundred feet or so . So if we 've got a a tiny hole not much water is going to get out . What does
[PS5R0]
No .
[PS5PY]
come out will be really sort of squirting out . But not much water will get through . When we had a great big hole in the bottom of the dam ,
[PS5R0]
More pressure .
[PS5PY]
a lot of water would come through . Well that hole is a bit like resistance .
[PS5R0]
Yeah .
[PS5PY]
Right , so if we 've got a lot of volts , so lot of volts , that gives a lot of current . And what 's current ? Current you can think of as the amount of water that actually gets through , the
[PS5R0]
Mm .
[PS5PY]
amount of the amount of electricity that actually gets through ,
[PS5R0]
Mm .
[PS5PY]
and the resistance . If we 've got high resistance , what do you think will happen with a high resistance ?
[PS5R0]
They 'll be a lot of current .
[PS5PY]
With a high resistance it 's resisting the current , it 's stopping the current .
[PS5R0]
Oh right , yeah .
[PS5PY]
Okay , so high resistance gives low current .
[PS5R0]
Low current .
[PS5PY]
And obviously a low resistance
[PS5R0]
Will give a high current .
[PS5PY]
gives a high current . A low resistance is a big hole . A high resistance is if there 's a tiny little peep hole
[PS5R0]
Yeah .
[PS5PY]
it was trying to force through that .
[PS5R0]
Yeah .
[PS5PY]
The current is you can think of it as the amount of water goes through , it 's actually the the current is the amount of electrons that get through in a second . So I 've got someone here on the outside of the dam counting the electrons as they go past . Well [UNCLEAR] lots through to day , cos there 's the big hole or there 's a lot of pressure . So if you have a lot of pr a lot of pressure , a lot of a lot of volts
[PS5R0]
Mm .
[PS5PY]
and a big hole which will give a low resistance , you get a terrific amount
[PS5R0]
Yeah .
[PS5PY]
going through . If you have a big hole but only tiny little voltage then you wo n't get much going through . So
[PS5R0]
So it 's er always the opposite .
[PS5PY]
Volts the more volts the more current .
[PS5R0]
Yeah .
[PS5PY]
But resistance , the more resistance
[PS5R0]
Stops it .
[PS5PY]
the less you get through .
[PS5R0]
Yeah .
[PS5PY]
So the current
[PS5R0]
reduces
[PS5PY]
the current is going to be something like multiplied by the voltage . Right . So if it 's got ten times the voltage , you 'll get ten ten times the current through . Which is why one and half volts you know wo n't do you much harm .
[PS5R0]
No .
[PS5PY]
But assuming your resistance stays the same , your resistance is about one mega [UNCLEAR] million ohms . So if your resistance stays the same and we keep increasing the voltage at some stage you say ooh it feels tingly
[PS5R0]
Mm .
[PS5PY]
ooh I do n't like that . That 's around erm sixty seventy volts you can say oh do n't like that , ninety volts [UNCLEAR] stop . Erm two forty volts [UNCLEAR]
[PS5R0]
[PS5PY]
So current times the voltage and then divide by the resistance , so current equals V over R ,
[PS5R0]
R.
[PS5PY]
you 've seen that before .
[PS5R0]
Yeah .
[PS5PY]
You do n't usually write C for current because it gets confused with lots of other like capacitance . So we use I . Erm
[PS5R0]
Yeah .
[PS5PY]
that 's [UNCLEAR] but that 's basically how electricity works . And it needs to have a path to get there and back . So you have a battery and two terminals on it . Then you have say this goes round to a light bulb [UNCLEAR] [UNCLEAR] amps
[PS5R0]
Mm .
[PS5PY]
Does n't light up . The electric you say oh the electricity can go round there and if it gets [UNCLEAR] light , [UNCLEAR]
[PS5R0]
No [UNCLEAR] it 's not it 's not connecting .
[PS5PY]
but ca n't flow through it and get back . So it 's not quite the same as this water analogy cos it 's got to have somewhere to go all the way round .
[PS5R0]
Yeah .
[PS5PY]
Which is why we call it a circuit . Okay ? Erm so if you can try to think about where is the circuit ? Where does it start off from , what what started the battery what pole of the battery . Can it get all the round and back to the [UNCLEAR] it 'll work .
[PS5R0]
Mm .
[PS5PY]
If it ca n't get all the way round cos someone 's pulled this wire out , or opened a switch
[PS5R0]
That 's a short
[PS5PY]
or
[PS5R0]
circuit , is n't it ?
[PS5PY]
It 's an open circuit .
[PS5R0]
Oh
[PS5PY]
It 's an open circuit if there 's a bit of a circuit missing .
[PS5R0]
Oh right , yeah .
[PS5PY]
Circuit is missing . A short circuit is when somebody takes a short cut . Now there 's the battery .
[PS5R0]
That 's fine , yeah .
[PS5PY]
Right , there 's the battery and electricity 's got to go we usually talk of positive current going round this way . Goes along here and through that big resistance , it 's a high resistance . Right ? So it 's a little a little tiny hole it 's trying to get through here .
[PS5R0]
Mm .
[PS5PY]
And it 's stopping it . Not much electricity 's getting back . You 've got a big [UNCLEAR] thick piece of wire across there , join it up . You 're not going to get much current down there at all .
[PS5R0]
No .
[PS5PY]
Most of it 's going to take the easy way short cut
[PS5R0]
[UNCLEAR]
[PS5PY]
because this sort of looks like , something about this big . That sort of pipe .
[PS5R0]
Yeah .
[PS5PY]
So for the the water to go down the current to flow through .
[PS5R0]
Mm .
[PS5PY]
So it 'll take the short cut , the easy way , making a short circuit . Wo n't go the long way round , a short circuit .
[PS5R0]
No .
[PS5PY]
Erm and if did that with a car battery , erm it 'll probably explode . I 've seen erm [UNCLEAR] a spanner , metal about that thick , vaporize , on the terminals of a car battery . It 's erm when you start a car , have you ever been in a car when someone 's started it up in gear and the car moves forward ?
[PS5R0]
Yeah .
[PS5PY]
Well that 's just the battery doing that .
[PS5R0]
Oh right .
[PS5PY]
So it 's got enough power stored in that battery to do that . And in a few in a fraction of a second , if you try and if you short it all out , give it a very you know great big wide pipe to rush through , the virtually the whole contents of the electricity of the battery tries to get through that , and a spanner is like that , very
[PS5R0]
Mm .
[PS5PY]
little resistance goes thorough there , heats the metal very rapidly , melts the metals and then turns the turns the molten metal into vapour
[PS5R0]
Mm .
[PS5PY]
and explodes . And usually the battery explodes .
[PS5R0]
Mm .
[PS5PY]
So do n't drop lumps of metal over batteries .
[PS5R0]
[PS5PY]
Very very dangerous .
[PS5R0]
Yeah .
[PS5PY]
Okay that 's the bit about electricity . Let's see
[PS5R0]
Alright .
[PS5PY]
where we can pick up some marks . Now tell me what erm what sort of preparation you did for this .
[PS5R0]
Well erm we had books like these , topics that we had to cover .
[PS5PY]
Yep .
[PS5R0]
And er I told Mum the other day that w in double science we 've still got to do one and a half topics . And she could n't believe it cos like , you know , now we 've got ta start down getting [UNCLEAR] some revision ,
[PS5PY]
Mm .
[PS5R0]
we 've still got ta do one and a half topics of these books . But erm I looked through the books and erm I wrote down notes and things like that , and I looked through my exercise book . And erm at the end they have er questions at the end of each topic .
[PS5PY]
Okay .
[PS5R0]
Which helps you . This is all about the solar system and that . And erm I just basically did that .
[PS5PY]
When you 're revising you said the other night , you cover the answers up and try the question . It 's erm really about the only way to do it on problems .
[PS5R0]
Yeah .
[PS5PY]
Because if you look at a problem , and you read through , have someone to work it out you say yeah yeah yeah yeah yeah , and that 's yeah obvious . Erm if you have the just the question , and you 've got to work it out , [UNCLEAR] it 's not so obvious .
[PS5R0]
Mm .
[PS5PY]
And it 's a good way to check if you know it . Right question number two . Nought . We 'll start with that one because because no because no one should get nought on a question I think . Because there 's always something even if you kno you think you know something you about it . A bit of common sense will usually give you some answers .
[PS5R0]
Mm .
[PS5PY]
Like erm people always know a lot more than they think they know . And they do n't want to put down what they do know cos they think it 's obvious .
[PS5R0]
Yeah .
[PS5PY]
But put it down , they get some marks .
[PS5R0]
We have n't done about [UNCLEAR] about circuits .
[PS5PY]
Ah , right .
[PS5R0]
See , Mum and I looked a bit up in my book [UNCLEAR]
[PS5PY]
Right . Each lamp is fifteen watt , thirty volts . They arrange them in series and plug them into the mains supply . Draw a diagram , you did n't .
[PS5R0]
No .
[PS5PY]
So you did n't get anything for that . [UNCLEAR]
[PS5R0]
[PS5PY]
What is the current through each lamp when they 're switched on . Show your working . Two forty volt . Now right okay . [UNCLEAR] That 's [UNCLEAR] definitely give you one for that .
[PS5PY]
All fuses can be bought . Which fuse should they put in the plug ?
[PS5R0]
I put thirteen .
[PS5PY]
Well ,
[PS5R0]
Mum said usually it 's three .
[PS5PY]
Well erm
[PS5R0]
Cos there 's a lot of [UNCLEAR] bulbs to light up , so I thought thirteen .
[PS5PY]
Looks [UNCLEAR]
[PS5R0]
Give it a higher [UNCLEAR]
[PS5PY]
It does it does n't really matter erm there 's only Give reasons for this choice . If stronger [UNCLEAR] circuits , [UNCLEAR] another bit of [UNCLEAR]
[PS5R0]
[PS5PY]
[UNCLEAR] Okay erm Protective device . What 's that oh is this the teacher 's ?
[PS5R0]
No I put that in yesterday .
[PS5PY]
Later . Right . A fuse is not an insulator okay ? It 's a conductor .
[PS5R0]
[PS5PY]
Right . A fuse again . It 's a deliberate weak link . Let's say you 're going to tow erm one car with another car . And you 've got this good towing rope , you do n't want it to snap . You know when towing ropes sometimes
[PS5R0]
Mm .
[PS5PY]
jerk [UNCLEAR] and they snap . So you have the towing rope and then you have a little bit of old rope that is weaker than your rope .
[PS5R0]
Mm .
[PS5PY]
And you use that somewhere in the and you tie that to one car and then join that up . So that if something breaks it 's going to be that weak old rope , not
[PS5R0]
Yeah .
[PS5PY]
going to be your new tow rope . Well you can think of it a bit like that . I was tel I was telling you looking at it from another point of view last night of the What happens when you put electricity through a wire ? May I pinch one of your cigarettes ? Ooh look at that .
[PS5R0]
Yeah . Oh Erm having to put electricity through a wire . Erm it 'll either stop the
[PS5PY]
Little bit of electricity and then make it more and more [UNCLEAR]
[PS5R0]
It will increase the electricity will increase through the wire .
[PS5PY]
Right . Okay . So you 're increasing the electricity , and what happens to the wire ?
[PS5R0]
Melt .
[PS5PY]
Right . Good . Before it melts I mean no we do n't normally melt the wires , what but what happens ? You notice the erm you 've got an electric fire running , what happens to the flex ?
[PS5R0]
The flex ? What 's the flex ?
[PS5PY]
The flexible connection .
[PS5R0]
[PS5PY]
The cable .
[PS5R0]
Erm
[PS5PY]
The wire that goes to it .
[PS5R0]
Well it wo n't wo n't work because it 'll be
[PS5PY]
It 's gets [UNCLEAR]
[PS5R0]
too hot .
[PS5PY]
So whenever electricity whenever electricity goes through a conductor , usually a wire , the wire gets warm .
[PS5R0]
Mm .
[PS5PY]
Erm the electricity every every bit of wire has got some resistance and erm electricity will be struggling through , warms it up . Er what happens in a light bulb , when you switch on ?
[PS5R0]
The electricity flows through and lights
[PS5PY]
[UNCLEAR]
[PS5R0]
the bulb up .
[PS5PY]
Why does it light up ?
[PS5R0]
Because electricity 's been there 's a bit in the bulb that
[PS5PY]
How does it how does it make light ? How does how does it light ?
[PS5R0]
The little bulb inside the actual glass bulb .
[PS5PY]
Right , something there 's something inside the glass bulb and what happens to it ?
[PS5R0]
Well electricity flows through it .
[PS5PY]
Right and what happens when electricity flows through this little coiled coil of wire ?
[PS5R0]
Lights up .
[PS5PY]
Why does it light up ?
[PS5R0]
I do n't know .
[PS5PY]
I mean the erm your hair dryer does n't light up when you put electricity through it , does it ? Have you ever seen your hair dryer light up ?
[PS5R0]
No .
[PS5PY]
You have actually I 'm sure . Have you ever looked down into the hair dryer ?
[PS5R0]
Heat .
[PS5PY]
Right and you see it red .
[PS5R0]
Yeah .
[PS5PY]
Especially if it 's if as when it first turns on or if the f the fan heater is not blowing very much . And the you see bits of the element glowing red , [UNCLEAR]
[PS5R0]
Mm .
[PS5PY]
If you if you do n't with a hair dryer if you were n't blowing the air over it , what happens ? Or say a fan heater erm a [UNCLEAR] fan heater in the bathroom
[PS5R0]
Mm .
[PS5PY]
It happened to that the other day . Erm as I say it turned the the element on but no fan blowing air over it to cool it [UNCLEAR]
[PS5R0]
Did it melt ?
[PS5PY]
Overheats and it would melt , so because of that they put a little protector thing on to cut out a thermal cut out to stop the current flowing
[PS5R0]
Mm .
[PS5PY]
or it would just melt . So light bulb , when you turn on it gets warm , then it gets hot , then it gets red hot , then it gets white hot . It gets so hot it 's giving off a lot of light erm light bulbs are hot to touch .
[PS5R0]
Mm .
[PS5PY]
Yes , so they 're
[PS5R0]
Yeah .
[PS5PY]
giving off heat and [UNCLEAR] quite a bit of that heat is coming off as light .
[PS5R0]
Right .
[PS5PY]
So they 're deliberately made so we get light out of them . Erm that 's ohm 's law is part of the question , question two . And to work out any of the volt or [UNCLEAR]
[PS5R0]
[PS5PY]
Right . Amps amps is current , right ?
[PS5R0]
Yeah .
[PS5PY]
So we 'll go back to Ohm 's law here . Current is volts divided by resistance . Right current in amps , let's give you two , volts and do you know what we measure resistance in ?
[PS5R0]
Erm no . I do know but I sh I should know .
[PS5PY]
Okay . On her majesty 's service . Ohms .
[PS5R0]
Ohms ! Yeah that 's it .
[PS5PY]
Called [UNCLEAR]
[PS5R0]
Yeah .
[PS5PY]
Who 's law it was . Now so on that one . Well [UNCLEAR] they give you they even give you fro from that by manipulating then equations you can derive other equations , you come up with other equations . That 's one of the equations that you come up with . Okay ? So current is equal to volt is equal to power divided by volt [UNCLEAR]
[PS5R0]
Mm .
[PS5PY]
Right . erm Current which one . How many marks next question ?
[PS5R0]
Three .
[PS5PY]
Okay . Erm [UNCLEAR] There 's quite a bit to go into with that but that 's hopefully given you some idea of how electricity works .
[PS5R0]
Mm .
[PS5PY]
The equations they will give you in the book are in that one . Erm they give it er you just have to know what power is . Power is the wattage .
[PS5R0]
Mm .
[PS5PY]
So erm [UNCLEAR] electric motors are measured in power . Wattage .
[PS5R0]
Mm .
[PS5PY]
Mopeds . You know when you 've got a moped , [UNCLEAR] plate on it ?
[PS5R0]
Mm .
[PS5PY]
And it 'll say so many kilowatts .
[PS5R0]
Mm .
[PS5PY]
[UNCLEAR]
[PS5R0]
[PS5PY]
It 's just a measurement of power .
[PS5R0]
Right .
[PS5PY]
So instead of measuring horsepower you 're measuring kilowatts . Erm okay . Let's have a look at two papers . Right , you 've got a lot of twos on that one . Couple of fives on this . Five on number five . Right again electricity here , you did n't get two marks [UNCLEAR] Electricity board could use wind generated power in several ways . So when there is n't any wind you can use the thermal power stations instead .
[PS5R0]
[UNCLEAR]
[PS5PY]
You 're something funny by using [UNCLEAR] . Sa saving [UNCLEAR]
[PS5R0]
Yeah .
[PS5PY]
Erm [UNCLEAR] I mean I would n't necessarily agree with all these markings because everybody who marks the markings are sometimes slightly different .
[PS5R0]
Yeah .
[PS5PY]
But erm that 's a that 's a reasonable answer . Two out of three . What fuels may be used in thermal power stations ? Two out of three there , so fossil fuels , nuclear reactor , wind and what 's the other energy source that you can use ? Well not wind .
[PS5R0]
Solar .
[PS5PY]
Yeah , what fuels need thermal power stations ?
[PS5R0]
Solar power .
[PS5PY]
Erm thermal is the fuel that you 're heating . So that 's like [UNCLEAR] Erm they use gas power stations as well .
[PS5R0]
Yeah .
[PS5PY]
So they 're probably looking for both fossil fuels which includes gas . Okay , so I think you 've got , definitely got the idea there .
[PS5R0]
Yeah .
[PS5PY]
That 's okay . Now are you alright on charts ? Bar charts ?
[PS5R0]
Yeah , if you turn over I 've got eighteen out of twenty two .
[PS5PY]
Brilliant . Good that 's good . Because that 's that 's a thing that will apply to all subjects . So if
[PS5R0]
Mm .
[PS5PY]
you 're good at that you can get marks in lots of subjects
[PS5R0]
Yeah I 'm I 'm alright on that .
[PS5PY]
just on that . Okay .
[PS5R0]
That was all about smoking so Oh yeah , what 's a load in a river ? I 've got a question
[PS5PY]
L O A D ?
[PS5R0]
Yeah , there .
[PS5PY]
Yeah .
[PS5R0]
I looked it up but I could n't
[PS5PY]
Erm if you look at a river that 's working run running quickly down from the mountains
[PS5R0]
Mm .
[PS5PY]
to the sea . It 's carrying with it a lot of soil , bits of rock ,
[PS5R0]
Mm .
[PS5PY]
that 's it 's load . [UNCLEAR]
[PS5R0]
I put the impact of the river , she did n't
[PS5PY]
Mm .
[PS5R0]
give me any marks [UNCLEAR]
[PS5PY]
No . No . It 's it 's also called the [UNCLEAR] . It 's what it carries down to the
[PS5R0]
Mm .
[PS5PY]
sea . When it gets to the sea , it slows down . When
[PS5R0]
Mm .
[PS5PY]
it slows down it drops a lot of the silt , mud and rocks . So higher up it 's dropping the rocks .
[PS5R0]
Mm .
[PS5PY]
As it gets slower and slower it can only carry smaller and smaller particles .
[PS5R0]
Mm .
[PS5PY]
By the time it gets to the sea then it 's slowed down a lot , it 's usually carrying very fine silt ,
[PS5R0]
Mm .
[PS5PY]
which it drops as mud . And the mud creeps out further and builds a delta
[PS5R0]
Mhm .
[PS5PY]
er the Nile delta or the Ganges or the Mississippi delta .
[PS5R0]
Yeah .
[PS5PY]
Okay so that 's what the load is . The
[PS5R0]
Right .
[PS5PY]
stuff that it 's
[PS5R0]
The stuff that
[PS5PY]
Just the load it 's
[PS5R0]
[UNCLEAR]
[PS5PY]
carrying along with .
[PS5R0]
Yeah .
[PS5PY]
Erm [UNCLEAR] So you could pick a few up a few marks on that . [UNCLEAR] Hmm . Yes , good answer . Take it to an expert who 'll tell you what 's happening . But the question is you have to design the experiment and you have to be the expert .
[PS5R0]
Oh yeah .
[PS5PY]
[UNCLEAR] So we get some crops and put a hedge [UNCLEAR]
[PS5R0]
[PS5PY]
Well I mean that 'll that might be worth a few marks .
[PS5R0]
Mm .
[PS5PY]
Erm yeah . Do n't give it anything to eat . Give it just cereal and see if it eats it . If it does n't [UNCLEAR] I 'm not touching that . [UNCLEAR] hedgehogs are obviously not eating the the wheat and the corn .
[PS5R0]
No .
[PS5PY]
Should be something else . But
[PS5R0]
Mm .
[PS5PY]
if it does start eating the wheat , well okay . Now we 'll give it a choice of a few other things ,
[PS5R0]
Mm .
[PS5PY]
and see if it eats it when he 's not starving . Erm [UNCLEAR] And on to the earth 's crust . Iron is one of the most important metals . So of the metals iron is very important , so is copper , because we use it a lot in circuits , erm
[PS5R0]
Is that right ? Write in a write a word equation to get [UNCLEAR] Is that right ?
[PS5PY]
Well an equation has an equals sign in it .
[PS5R0]
Oh right , yeah .
[PS5PY]
So it 's one thing plus it 's the in this case it 's iron plus oxygen gives iron oxide .
[PS5R0]
Oh right , okay , yeah .
[PS5PY]
Erm so it 'll be F E plus O two will give F E two O three
[PS5R0]
Yeah .
[PS5PY]
erm or F E three O four . There are
[PS5R0]
Mm .
[PS5PY]
two types of iron oxide . Erm so you just say the symbol . First of all you just think of it in words , [UNCLEAR] the iron plus the oxygen gives iron oxide . If
[PS5R0]
Okay .
[PS5PY]
you wrote that erm well for one mark , you 'd probably would n't get
[PS5R0]
Probably get
[PS5PY]
anything because you want the you they want the equation
[PS5R0]
They want the Yeah .
[PS5PY]
[UNCLEAR] what three things can be done to prevent it ? Erm keep it dry , keep it covered , erm
[PS5R0]
I put it [UNCLEAR]
[PS5PY]
I would n't have given you the mark for covered . Definitely a mark for dry . What do you mean by covered ? You usually say erm protected by paint or galvanized .
[PS5R0]
Yeah .
[PS5PY]
But it needs to be you need to have oxygen and you need water . Keep it away from oxygen is another one . Make sure there 's no air around that 'll stop it rusting .
[PS5R0]
Right .
[PS5PY]
Iron ore . Right . [UNCLEAR] iron ore , it comes up every year , erm an alloy . Right . An alloy is when you 've got two or more metals mixed together . So
[PS5R0]
Right
[PS5PY]
erm bronze is copper and tin . [UNCLEAR] an alloy is best when it combines the best of it 's component metals . Now we do n't we do n't need to work with iron . The thick frying pan is cast iron . It 's black because it 's still got a lot carbon in it . And
[PS5R0]
Right .
[PS5PY]
it 's brittle . If you hit that hard with your hammer , it 'll just break .
[PS5R0]
Yeah .
[PS5PY]
Erm a steel pan , if you hit it with a hammer , it 'll dent .
[PS5R0]
Mm .
[PS5PY]
So stainless steel , is an alloy of iron . Two reasons [UNCLEAR] pure iron to make car exhaust pipes . Right , there 's an easy two marks . At least an easy one mark . Why is stainless steel called stainless ? Have you seen stainless steel sinks ?
[PS5R0]
Yeah .
[PS5PY]
Okay . Do they rust ?
[PS5R0]
No .
[PS5PY]
So why might it be a good idea to use stainless steel for a car exhaust pipe ?
[PS5R0]
Because it wo n't rust then .
[PS5PY]
So you wo n't be replacing your exhaust
[PS5R0]
Well yeah .
[PS5PY]
every year cos it wo n't rust away if it 's stainless steel . Erm okay , [UNCLEAR] Right . Fancy a [UNCLEAR] What would you do to produce a movement of the ammeter needle ? Turn the switch on . [UNCLEAR] size of the movement more coils put more batteries . What would you do to reverse the direction of the ammeter needles first movement , B ? You would n't reduce the batteries to reverse it to make it go the other way . You 'll reverse the battery . Turn the battery round the other way
[PS5R0]
Oh right , yeah .
[PS5PY]
in the circuit and then the needle will jump the other way .
[PS5R0]
Yeah .
[PS5PY]
Three marks here . Electric currents . Induce currents , transformers work by induced currents , pick out appliances that use for [UNCLEAR] transformer . Okay a [UNCLEAR] pack is one . Erm a drill , electric toothbrush probably use a transformer because you want to lower it er an electric shaver would use a transformer . You I think these are what would you run off a transformer . So reading lamp , toothbrush and three marks so we 're looking for three of them . Electric
[PS5R0]
Yeah .
[PS5PY]
shaver you run off [UNCLEAR] and a toothbrush .
[PS5R0]
Yeah .
[PS5PY]
Erm things you would and you would n't want them connected to the mains , stuck in your mouth .
[PS5R0]
Yeah .
[PS5PY]
[UNCLEAR]
[PS5R0]
Right .
[PS5PY]
So some of them you can work out buy if you know what a transformer does , it steps down all of the current , it reduces the voltage .
[PS5R0]
Mm .
[PS5PY]
So instead of dealing with sort of high [UNCLEAR] trying to push everything [UNCLEAR] So if you bring your voltage down from two forty volts to say you could get a a transformer , a battery eliminator , for a tape recorder . If you that runs on one and a half volts .
[PS5R0]
Mm .
[PS5PY]
Three volts sorry , three volts . So plug two forty volts into that , just not
[PS5R0]
Mm .
[PS5PY]
[UNCLEAR] transformer to bring it down to a lower voltage . So lots of things like that it transforms .
[PS5R0]
Right .
[PS5PY]
Erm
[PS5R0]
That one I that second paper she put the answers in so [UNCLEAR]
[PS5PY]
Okay .
[PS5R0]
my teacher put the answers in .
[PS5PY]
Erm right . A number of materials including metals are superconductors at very low temperatures . They 've got very low conducting 's the opposite of resistance so the good conductors [UNCLEAR]
[PS5R0]
You have a look at the chart . Mum seems to think I was right .
[PS5PY]
Right , What is the crit the critical temperature of superconductor wiring ?
[PS5R0]
Oh no , not that one . I 've got the wrong one , sorry .
[PS5PY]
So minus a hundred and twenty there I mean that 's they 're just the there 's not a lot of difference really . Oh no , that 's not right . I
[PS5R0]
No .
[PS5PY]
would n't give you any marks for that .
[PS5R0]
No .
[PS5PY]
Because you did n't put the minus in .
[PS5R0]
Yeah .
[PS5PY]
That 's why .
[PS5R0]
There 's a chart in here , hang on .
[PS5PY]
[UNCLEAR]
[PS5R0]
No it 's in this one . There 's a chart and Mum seems to there it is . Read that then and I I put forty two .
[PS5PY]
Right . Four weeks January seventy eight , windmills and electricity demand in California , four weeks of January . So that 's the electricity demand . And that 's the power [UNCLEAR] What 's the highest [UNCLEAR] for Jan seventy eight . So the highest [UNCLEAR] forty two . [UNCLEAR] erm forty one , [UNCLEAR] forty two [UNCLEAR]
[PS5R0]
It does n't go [UNCLEAR]
[PS5PY]
Right [UNCLEAR] forty forty two . [UNCLEAR] forty two , [UNCLEAR] maybe forty three but it 's very close especially that they have n't given any scale
[PS5R0]
No .
[PS5PY]
to read it . So that 's the electricity per [UNCLEAR] so that 's fine .
[PS5R0]
Yeah , but I got that bit wrong
[PS5PY]
Forty two .
[PS5R0]
[PS5PY]
Okay well they get they 've got lots of them to mark and they marked quickly but I [UNCLEAR] Looks alright to me that .
[PS5R0]
Hmm . Sorry , I just wanted your opinion I mean .
[PS5PY]
[UNCLEAR] Mm . I mean it might be wrong but I ca n't see [UNCLEAR]
[PS5R0]
[PS5PY]
Okay . You do n't know much about heptane and ethanols
[PS5R0]
Oh no .
[PS5PY]
things . Right erm oh it 's a bit late to get into organic chemistry
[PS5R0]
Yeah .
[PS5PY]
so I 'll [UNCLEAR]
[PS5R0]
[UNCLEAR]
[PS5PY]
Now are these [UNCLEAR]
[PS5R0]
Yeah , her marks were [UNCLEAR]
[PS5PY]
Complete complete combustion of ethanol . Erm Still have n't got any oxygen . That should be a plus , that 's what 's wrong with it .
[PS5R0]
Mm .
[PS5PY]
So should have put a plus there . Ethanol plus oxygen gives carbon dioxide , water .
[PS5R0]
Right .
[PS5PY]
Erm so [UNCLEAR] change that . This is your paper is n't it ?