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Author Topic: Edexcel PHYSICS Doubts  (Read 137733 times)

Offline Saladin

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Re: Edexcel PHYSICS Doubts
« Reply #15 on: May 10, 2010, 06:38:35 pm »
You are talking abt mj 2009 3b rite?

Ok,

The mean:
\frac{14.2+14.7+15.1}{3}=14.7

Now find the maximum difference:
15.1-14.7=0.4
14.7-14.2=0.5

So, the maximum uncertainty is \pm0.5 GPa
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Offline Ascer Zayan

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Re: Edexcel PHYSICS Doubts
« Reply #16 on: May 10, 2010, 07:23:07 pm »
Quote from: The Mysterious Dude on May 10, 2010, 06:38:35 pm
You are talking abt mj 2009 3b rite?

Ok,

The mean:
\frac{14.2+14.7+15.1}{3}=14.7

Now find the maximum difference:
15.1-14.7=0.4
14.7-14.2=0.5

So, the maximum uncertainty is \pm0.5 GPa
Wat About part C in this exam i dont understand at allllllllllllll
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Offline T.Q

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Re: Edexcel PHYSICS Doubts
« Reply #17 on: May 10, 2010, 08:16:08 pm »
Quote from: Ascer Zayan on May 10, 2010, 07:23:07 pm
Wat About part C in this exam i dont understand at allllllllllllll

Value is in GPa, G means 10^9, so yes
10^(10) can mean anything from 5.0 x 10^9 to 4.9 x10^(10)so my answer is within range
« Last Edit: May 10, 2010, 08:17:58 pm by T.Q »
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Offline Ascer Zayan

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Re: Edexcel PHYSICS Doubts
« Reply #18 on: May 11, 2010, 06:19:47 am »
Quote from: T.Q on May 10, 2010, 08:16:08 pm
Value is in GPa, G means 10^9, so yes
10^(10) can mean anything from 5.0 x 10^9 to 4.9 x10^(10)so my answer is within range
Welll Do u Understand?
10^(10) can mean anything from 5.0 x 10^9 to 4.9 x10^(10
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Offline Saladin

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Re: Edexcel PHYSICS Doubts
« Reply #19 on: May 11, 2010, 10:23:09 am »
Quote from: break freak on May 11, 2010, 10:21:28 am
the precision is the least value that can be measured. Example: for these values 12.0,12.5,13.0 the precision is 0.5
but in our case 14.2 14.7 15.1 the precision is 0.1 8)

I am not too sure about that. The limits of accuracy for this is said in the mark-scheme to be 0.5
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Offline break freak

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Re: Edexcel PHYSICS Doubts
« Reply #20 on: May 11, 2010, 10:25:34 am »
Quote from: 7ood on May 08, 2010, 03:45:23 pm
how to get the Precision though??
the precision is the least value that can be measured. Example: for these values 12.0,12.5,13.0 the precision is 0.5
but in our case 14.2 14.7 15.1 the precision is 0.1  ;D
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Offline Saladin

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Re: Edexcel PHYSICS Doubts
« Reply #21 on: May 11, 2010, 10:40:52 am »
Quote from: break freak on May 11, 2010, 10:25:34 am
the precision is the least value that can be measured. Example: for these values 12.0,12.5,13.0 the precision is 0.5
but in our case 14.2 14.7 15.1 the precision is 0.1  ;D

O ok, but the question asked something different. O well.
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Offline vanibharutham

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Re: Edexcel PHYSICS Doubts
« Reply #22 on: May 11, 2010, 10:42:23 am »
Just a note,

On the May/June 2009 Paper

Question 4,

the one with the potential difference across the diode,

the mark scheme seems to have a mistake, because it misses out question 3b)

The answer to question 4 needs to be A

It can't be D because the diode is reverse biased.
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Offline T.Q

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Re: Edexcel PHYSICS Doubts
« Reply #23 on: May 11, 2010, 10:49:01 am »
Quote from: vanibharutham on May 11, 2010, 10:42:23 am
Just a note,

On the May/June 2009 Paper

Question 4,

the one with the potential difference across the diode,

the mark scheme seems to have a mistake, because it misses out question 3b)

The answer to question 4 needs to be A

It can't be D because the diode is reverse biased.

yes thats true, THE ans should be A
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Offline Saladin

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Re: Edexcel PHYSICS Doubts
« Reply #24 on: May 11, 2010, 10:52:58 am »
Quote from: vanibharutham on May 11, 2010, 10:42:23 am
Just a note,

On the May/June 2009 Paper

Question 4,

the one with the potential difference across the diode,

the mark scheme seems to have a mistake, because it misses out question 3b)

The answer to question 4 needs to be A

It can't be D because the diode is reverse biased.

I knew it! I wrote down A as well. It just had to be!
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Offline Ascer Zayan

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Re: Edexcel PHYSICS Doubts
« Reply #25 on: May 11, 2010, 12:24:19 pm »
Quote from: The Mysterious Dude on May 08, 2010, 03:56:42 pm
This is what you have to do.

1. Find the mean
2. Then find the difference between the mean and the highest value
3. \frac{Difference between two values}{mean}*100
This is to find Percentage of Uncertainty right??????
cuz i am losstttttt in physics Unit 3 :(
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Offline Saladin

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Re: Edexcel PHYSICS Doubts
« Reply #26 on: May 11, 2010, 01:08:24 pm »
Quote from: Ascer Zayan on May 11, 2010, 12:24:19 pm
This is to find Percentage of Uncertainty right??????
cuz i am losstttttt in physics Unit 3 :(

No, in the markscheme, it says that you have to find it in GPa. I know this paper had a bad mark scheme.
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Offline 7ooD

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Re: Edexcel PHYSICS Doubts
« Reply #27 on: May 11, 2010, 01:56:45 pm »
i dnt get question 4 lool my teacher answered it A but in markscheme D i kno but i think they have some idea that a diode cant always stop current from passing like for example we have to apply a great voltage in order it pass current we need astarphysicsandmaths to finish this :D
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Offline vanibharutham

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Re: Edexcel PHYSICS Doubts
« Reply #28 on: May 11, 2010, 02:17:13 pm »
A diode is a device that only allows current to flow in one direction. That is why it is used in rectification i.e.  changing AC to DC.

When a diode is forward biased it will allow current to pass through, as in 4 A

However, when a diode is reverse biased it will not allow current to pass through, as in 4 D

to completely understand how diodes work would go past the A level syllabus as you would need to understand P and N type semi conductor doping and then valence and conduction bands. With that, you will be able to explain why the diode conducts in one direction.

But for A level just know that if the anode of a diode is connected to the positive terminal of a power supply it is considered Forward Biased and will allow conduction.
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Offline Darth Austrakast

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Re: Edexcel PHYSICS Doubts
« Reply #29 on: May 11, 2010, 03:32:45 pm »
Quote from: Austrakast on May 08, 2010, 04:05:09 pm
here's a question i need help solving:
A student observes the diffraction of white light by holding a diffraction grating close to her eyes
a)draw a simple diagram to illustrate what the student observes
b) a tube of KMn04 solution is placed in front of white light source.Then the student views the filament through the solution with the grating close to her eyes. she notices that the blue, yellow and orange colors have vanished. Give an explanation.

Can you please help me asap? Thanks ! :)

can't anyone solve this question? ???
it would be really helpful...............exams are less than 24 hours away!
so please help
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