Important question please help for physics exam tomorrow

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John10000
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Basically on the AQA past paper it says:

The resistance of the metal filament inside the bulb increases as the potential difference across the bulb increases.

Explain why.

My answer:

The increased potential difference means an increased current will flow through the metal filament, as it does, some of the electrical energy is transferred to heat energy which heats up the metal filament and makes the metal ions vibrate faster making it more difficult for the electrical charge to flow through, therefore the resistance increases.


AQA Mark scheme:


metals contain free electrons (and 1
ions)
as temperature of filament increases 1
ions vibrate faster / with a bigger
amplitude


electrons collide more (frequently) 1
with the ions
or
(drift) velocity of electrons
decreases




Would i get it wrong for my answer? Ive learnt that from the AQA approved books!?! Please help and give me advice on this!!!
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Jacobisswaggy
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How many marks is it? 3?
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Magistl
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It's an alright question, but it doesn't have specific key words that are for the marks. 1/3
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John10000
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(Original post by Jacobisswaggy)
How many marks is it? 3?

Yeah 3 mark question, i wrote (three 1's on the aqa mark scheme but its not clear sorry), would i not get any marks for it?
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John10000
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(Original post by Magistl)
It's an alright question, but it doesn't have specific key words that are for the marks. 1/3

I know but what im saying is different? I dont really understand why the AQA mark scheme is talking about the metal electrons? i thought all we need to know is the ions vibrate faster making it harder for electrical charges to flow through increasing the resistance.

?
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Magistl
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(Original post by John10000)
Yeah 3 mark question, i wrote (three 1's on the aqa mark scheme but its not clear sorry), would i not get any marks for it?
You'd get 1/3, as I stated.
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Phteven
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(Original post by John10000)
I know but what im saying is different? I dont really understand why the AQA mark scheme is talking about the metal electrons? i thought all we need to know is the ions vibrate faster making it harder for electrical charges to flow through increasing the resistance.

?
Electrons are electrical charges, as far as I know. It's harder for the electrons to get through.

Do you remember the equation I=Q/t, the Q is charge and you work it out by multiplying the number of electrons that move through a given point by the charge of an electron. Do you remember doing that? That's because it's the flow of electrons that generates the current.

You do know everything you need to know. You're just using 'electrical charges' instead of electrons.

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John10000
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(Original post by Magistl)
You'd get 1/3, as I stated.
Ok which leads me to my next question how do I get 3/3? lol. Do I just write what the mark scheme said for all questions regarding increasing resistance as the current/p.d across the component increases?
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Magistl
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(Original post by John10000)
I know but what im saying is different? I dont really understand why the AQA mark scheme is talking about the metal electrons? i thought all we need to know is the ions vibrate faster making it harder for electrical charges to flow through increasing the resistance.?
They talk about the electrons interacting with the metal ions that make the resistance. Let me give you a good example answer,

As the resistance increases, the potential difference increases due to the vibrating ions colliding with the free metal electrons that encompasses the metal - this causes a frequent collision between the electrons and the ions.

This is 3/3, it's direct, professional and adheres to the specific mark scheme. Unfortunately, GCSE science is awfully picky about key words.
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John10000
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(Original post by StephenNaulls)
Electrons are electrical charges, as far as I know. It's harder for the electrons to get through.

Do you remember the equation I=Q/t, the Q is charge and you work it out by multiplying the number of electrons that move through a given point by the charge of an electron. Do you remember doing that? That's because it's the flow of electrons that generates the current.

You do know everything you need to know. You're just using 'electrical charges' instead of electrons.

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Ok so for this question it would be the ions vibrate faster colliding with the electrons more making it more difficult for them to pass and therefore increasing the resistance?
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John10000
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(Original post by Magistl)
They talk about the electrons interacting with the metal ions that make the resistance. Let me give you a good example answer,

As the resistance increases, the potential difference increases due to the vibrating ions colliding with the free metal electrons that encompasses the metal - this causes a frequent collision between the electrons and the ions.

This is 3/3, it's direct, professional and adheres to the specific mark scheme. Unfortunately, GCSE science is awfully picky about key words.
Oh ok, so wait, so tell me if im correct, because i think this misunderstanding stems from a lack of understanding of the tricky way its put in the books,

current is the flow of electrical charge, it flows freely along a wire (current is NOT electrons, just electrical charge), then as it flows through the metal filament, the metals free electrons carry the electrical charges across (is that correct so far?)

And then the metal ions vibrate faster, increasing the collisions and the resistance.


PLEASE TELL ME IM RIGHT ABOUT THE WAY THE ELECTRICAL CHARGE FLOWS ALONG THE WIRE in terms of as just electrical charge
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Magistl
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(Original post by John10000)
Oh ok, so wait, so tell me if im correct, because i think this misunderstanding stems from a lack of understanding of the tricky way its put in the books,

current is the flow of electrical charge, it flows freely along a wire (current is NOT electrons, just electrical charge), then as it flows through the metal filament, the metals free electrons carry the electrical charges across (is that correct so far?)

And then the metal ions vibrate faster, increasing the collisions and the resistance.


PLEASE TELL ME IM RIGHT ABOUT THE WAY THE ELECTRICAL CHARGE FLOWS ALONG THE WIRE in terms of as just electrical charge
In my book it states that current is the flow of electrons. Hence, the vibrating ions colliding with the free metal electrons come to mind. You may very well be right, but if the key words aren't there, you'll not get the marks - GCSE doesn't care if you have the knowledge, they want to see only keywords.
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John10000
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(Original post by Magistl)
In my book it states that current is the flow of electrons. Hence, the vibrating ions colliding with the free metal electrons come to mind. You may very well be right, but if the key words aren't there, you'll not get the marks - GCSE doesn't care if you have the knowledge, they want to see only keywords.
Lol thats the thing, i have the knowledge, but like you said keywords.

Key words for most of the questions is fine, its pretty much this one that has stumped me. So if i get a question regarding this ill just remember:

Metals have free electrons, electrical energy is transferred to heat energy, this heats up the metal, making the metal ions vibrate faster and increasing the frequency of collisions between metal ions and electrons, increasing the resistance.


Thanks for your help mate (Y)
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Magistl
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(Original post by John10000)
Lol thats the thing, i have the knowledge, but like you said keywords.

Key words for most of the questions is fine, its pretty much this one that has stumped me. So if i get a question regarding this ill just remember:

Metals have free electrons, electrical energy is transferred to heat energy, this heats up the metal, making the metal ions vibrate faster and increasing the frequency of collisions between metal ions and electrons, increasing the resistance.


Thanks for your help mate (Y)
GCSE is primarily half-truths, throw your knowledge out of the window when approaching the exams and study the keywords religiously. That's usually how it works - given from what I've come to learn, A-level actually wants knowledge to be present. Good luck tomorrow.
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John10000
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Wait i remember now, conventional current is the flow of ELECTRICAL CHARGE from the positive to the negative terminal of the power supply, WHEREAS the FLOW OF ELECTRONS is from negative to positive
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John10000
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(Original post by Magistl)
GCSE is primarily half-truths, throw your knowledge out of the window when approaching the exams and study the keywords religiously. That's usually how it works - given from what I've come to learn, A-level actually wants knowledge to be present. Good luck tomorrow.
What do you mean knowledge to be present? As long as the concept is right for A-levels you get the mark regardless of keywords?


Thanks
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Magistl
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(Original post by John10000)
What do you mean knowledge to be present? As long as the concept is right for A-levels you get the mark regardless of keywords? Thanks
A-level wants you to present intelligence and knowledge. Although still picky over keywords, I believe A-level is equivalent to six mark type questions. Of course more difficult, but fixate on what is known, keyword and knowledge alike.
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John10000
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(Original post by Magistl)
A-level wants you to present intelligence and knowledge. Although still picky over keywords, I believe A-level is equivalent to six mark type questions. Of course more difficult, but fixate on what is known, keyword and knowledge alike.

Oh ok. Thanks
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Phteven
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(Original post by John10000)
Ok so for this question it would be the ions vibrate faster colliding with the electrons more making it more difficult for them to pass and therefore increasing the resistance?
Yes.


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