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AQA Physics PHYA4 - Thursday 11th June 2015 [Exam Discussion Thread] Watch

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    (Original post by Scottyyjones)
    Hey has anyone done their A2 ISA yet? Couldn't find a thread so thought I'd post it in here
    Nop, wen is urs?
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    (Original post by SmartIndianMan)
    Nop, wen is urs?
    Mine's tomorrow mate, on investigating the affect of resistors in series or parallel on the charge/discharge of a capacitor (or something along those lines)
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    (Original post by Lau14)
    Thanks I'm not too worried, I'm already revising far better this year than ever before!
    Wish I could say the same! I vow that when this coursework is complete I'll go into revision mode. Hold me to that promise!


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    (Original post by Scottyyjones)
    Hey has anyone done their A2 ISA yet? Couldn't find a thread so thought I'd post it in here
    I know of no one who has done theirs yet. I'm going to be doing the EMPA anyway but either way that's not complete either.

    I was thinking of creating an ISA/EMPA thread for this year as well but I decided against it as it would probably encourage cheating.


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    (Original post by CD223)
    Wish I could say the same! I vow that when this coursework is complete I'll go into revision mode. Hold me to that promise!


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    I'll be sitting here reminding you of all the things you should be doing :P
    Found my EMPA booklet thing, mostly technical bits but could be useful so I'll type it up tomorrow (Broadchurch is on now!)
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    (Original post by Lau14)
    I'll be sitting here reminding you of all the things you should be doing :P
    Found my EMPA booklet thing, mostly technical bits but could be useful so I'll type it up tomorrow (Broadchurch is on now!)
    Not gonna lie that sounds like a plan. Reminders on here will mean even when I TRY to procrastinate I'll be reminded.

    Oh nice! Thank you so much for agreeing to that - it'll be such a help! Oh yes, gotta love Broadchurch


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    (Original post by CD223)
    Not gonna lie that sounds like a plan. Reminders on here will mean even when I TRY to procrastinate I'll be reminded.

    Oh nice! Thank you so much for agreeing to that - it'll be such a help! Oh yes, gotta love Broadchurch


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    Yep, we can keep each other on track on tsr hopefully!

    It was the finale as well aaaahhhhhhh nope
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    (Original post by Lau14)
    Yep, we can keep each other on track on tsr hopefully!

    It was the finale as well aaaahhhhhhh nope
    Ahah. I can see this working I know! What a distraction from the thermal physics homework due tomorrow! Ahahaha


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    (Original post by CD223)
    Ahah. I can see this working I know! What a distraction from the thermal physics homework due tomorrow! Ahahaha


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    Well, we can try! Ah well... missing homework isn't the end of the world?
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    The possibly very useful EMPA guide: derived from our college's AS EMPA booklet. (Disclaimer, this means things may not be necessary or applicable for this year, but as far as I can see everything is relevant and I've checked exam lengths and marks)

    It covers practical/data handling skills needed for the two practical tasks of the EMPA (spoiler tags because it's long!)



    Spoiler:
    Show
    Physics Practical Work – A2 EMPA

    There are two assessed practical sessions (tasks 1 and 2), each one hour long and carried out in lessons under exam conditions, and a written section (duration: 1hr 15). The total mark for the EMPA is 55, with mark distribution varying very slightly between the three parts – usually 15-16 for each practical task and 23-24 or so for the written section. The EMPA is worth 60 UMS (half as much as the other papers, 20% of the year).

    There are four written papers available (June 2010-2013) on the AQA website, but the practical sections are only available from 2013.


    Measuring instruments – range and precision

    The range of a measuring instrument is the lowest and highest reading it can measure (e.g. a thermometer may measure -20 to 100°C).

    The precision of a measuring instrument is one scale division (this term may be used differently in other subjects, this is the definition for AQA Physics), e.g. the precision of the thermometer may be ±1°C. Usually given as a ± value, but the ± might be omitted sometimes.

    Significant figures

    Any reading you take must be given to the correct number of significant figures (e.g. when measuring with a ruler of precision ±0.001m, the reading of half a metre must be written as 0.500, not as 0.5. 50.0cm and 500mm is also acceptable, as long as your units are correct and consistent).


    Dependent and independent variables

    The independent variable readings are those chosen by you (or the ones you are told to take) before carrying out the experiment.
    The dependent variable readings are those that you measure. You must take a repeat reading of this.
    E.g. if you are looking at V/I characteristics you could set voltage to particular values and then measure the current. The voltage is the independent and the current is the dependent variable.


    Recording your results

    There are at least 5 marks available for this in total.

    Two marks are for drawing a results table with a ruler and having the independent variable in the left hand column.
    Include a separate column for any values calculated to plot a graph (e.g. if you have to plot a graph of 1/x but you’ve measured x, add a column for 1/x).

    There are two marks for using the correct number of significant figures for every reading (see above).
    There is another mark for including all units in the table headings. Use either the name of the unit in full or the accepted abbreviation.


    Graph plotting

    There are at least 9 marks available for this.
    The origin does not have to be included unless proportionality is to be shown. If the origin is included mark on both “0”s.

    Choose a scale so that the points cover more than 50% of each axis of A4 graph paper (28x20cm), so horizontal separation of first and last points must not be less than 10cm and vertical separation of first and last points must not be less than 14cm. There are 2 marks available for this. Also pick a scale that is easy to plot and take readings for (e.g. 1cm = 10 units, 2 units or 4 units. Not 1cm = 3 units or 7 units).

    Label both axes of the graph and include the units. There are 2 marks for doing this correctly.

    All points must be accurately plotted (within a distance of 1mm or less from the correct position) with “x” or “+”. There are 3 marks for this (check it!).

    Most graphs will be straight lines. There will be 1 mark for drawing a line of best fit correctly. It should have approximately equal numbers of points on either side of the line, and shouldn’t be influenced by obviously anomalous results. Anomalous results should be indicated if ignored. If the plotted points suggest a curve, a smooth curve should be drawn.

    You may have to find the gradient of graphs. Mark on the graph a large triangle that takes up most of the graph (each side should be minimum 8cm). Write on the triangle the value of the height and the value of the base with the units of each. The gradient = height/base, and the units of the gradients are units of height/units of base.

    Where an intercept is required it can either be read directly from the graph, or a suitable calculation may be required.


    Random errors

    Random errors are always present when an experiment is carried out. They can be reduced or minimised but never removed entirely. They are also described as the uncertainty in the measurement. They can be reduced by taking repeat readings. E.g. a measurement of length using a metre ruler can be given as (25.6 ± 0.1)cm. The units must be included.

    Uncertainty in the measurement from a set of results (e.g. a measurement is repeated 8 times to give 8 values for the length) can be found by first calculating the mean. However, this cannot be given to a higher number of significant figures than the original values. Then find the difference between the mean and the furthest away value and ± it.

    E.g. 8 readings of diameter of a wire are measured with a micrometer to the nearest 0.01mm
    0.30, 0.28, 0.29, 0.27, 0.28, 0.26, 0.31

    The values are all different, but not because a mistake has been made. The micrometer is only capable of giving readings to ±0.01mm, so this would be the error even if all readings were the same. There is also a small variation in the diameter of the wire.

    The mean of these values is 0.2825mm, 0.28mm to the correct number of significant figures. The smallest reading is 0.28mm, and the largest is 0.31mm. The differences between these and the mean are 0.02 and 0.03mm, so the diameter is (0.28 ± 0.03)mm.

    Minimum uncertainty – as mentioned above, there is always an uncertainty in each and every measurement and if there is no variation in readings then the uncertainty is the precision of the measuring instrument.


    Percentage uncertainty

    The most accurate reading is the one with the smallest percentage uncertainty. % uncertainty = (actual uncertainty/reading) x 100.


    Systematic errors

    Systematic errors affect all readings by the same amount and are usually “zero errors”, for example:

    Zero errors in meters. This is where the meter doesn’t read zero when disconnected. Corrections can be made by adding or subtracting the required amount. E.g. if an ammeter reads +0.01A, 0.01A must be subtracted from every reading.

    Zero errors in other measuring instruments. This is where the instrument does not read zero even when the reading should obviously be zero. E.g. a micrometer that has been “zeroed” properly should read 0.000 when the jaws are tightened with nothing in between them. If they do not read 0.000, there is a zero error which can be corrected in the same way.
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    (Original post by Lau14)
    Well, we can try! Ah well... missing homework isn't the end of the world?
    (Original post by Lau14)
    The possibly very useful EMPA guide: derived from our college's AS EMPA booklet. (Disclaimer, this means things may not be necessary or applicable for this year, but as far as I can see everything is relevant and I've checked exam lengths and marks)

    It covers practical/data handling skills needed for the two practical tasks of the EMPA (spoiler tags because it's long!)



    Spoiler:
    Show
    Physics Practical Work – A2 EMPA

    There are two assessed practical sessions (tasks 1 and 2), each one hour long and carried out in lessons under exam conditions, and a written section (duration: 1hr 15). The total mark for the EMPA is 55, with mark distribution varying very slightly between the three parts – usually 15-16 for each practical task and 23-24 or so for the written section. The EMPA is worth 60 UMS (half as much as the other papers, 20% of the year).

    There are four written papers available (June 2010-2013) on the AQA website, but the practical sections are only available from 2013.


    Measuring instruments – range and precision

    The range of a measuring instrument is the lowest and highest reading it can measure (e.g. a thermometer may measure -20 to 100°C).

    The precision of a measuring instrument is one scale division (this term may be used differently in other subjects, this is the definition for AQA Physics), e.g. the precision of the thermometer may be ±1°C. Usually given as a ± value, but the ± might be omitted sometimes.

    Significant figures

    Any reading you take must be given to the correct number of significant figures (e.g. when measuring with a ruler of precision ±0.001m, the reading of half a metre must be written as 0.500, not as 0.5. 50.0cm and 500mm is also acceptable, as long as your units are correct and consistent).


    Dependent and independent variables

    The independent variable readings are those chosen by you (or the ones you are told to take) before carrying out the experiment.
    The dependent variable readings are those that you measure. You must take a repeat reading of this.
    E.g. if you are looking at V/I characteristics you could set voltage to particular values and then measure the current. The voltage is the independent and the current is the dependent variable.


    Recording your results

    There are at least 5 marks available for this in total.

    Two marks are for drawing a results table with a ruler and having the independent variable in the left hand column.
    Include a separate column for any values calculated to plot a graph (e.g. if you have to plot a graph of 1/x but you’ve measured x, add a column for 1/x).

    There are two marks for using the correct number of significant figures for every reading (see above).
    There is another mark for including all units in the table headings. Use either the name of the unit in full or the accepted abbreviation.


    Graph plotting

    There are at least 9 marks available for this.
    The origin does not have to be included unless proportionality is to be shown. If the origin is included mark on both “0”s.

    Choose a scale so that the points cover more than 50% of each axis of A4 graph paper (28x20cm), so horizontal separation of first and last points must not be less than 10cm and vertical separation of first and last points must not be less than 14cm. There are 2 marks available for this. Also pick a scale that is easy to plot and take readings for (e.g. 1cm = 10 units, 2 units or 4 units. Not 1cm = 3 units or 7 units).

    Label both axes of the graph and include the units. There are 2 marks for doing this correctly.

    All points must be accurately plotted (within a distance of 1mm or less from the correct position) with “x” or “+”. There are 3 marks for this (check it!).

    Most graphs will be straight lines. There will be 1 mark for drawing a line of best fit correctly. It should have approximately equal numbers of points on either side of the line, and shouldn’t be influenced by obviously anomalous results. Anomalous results should be indicated if ignored. If the plotted points suggest a curve, a smooth curve should be drawn.

    You may have to find the gradient of graphs. Mark on the graph a large triangle that takes up most of the graph (each side should be minimum 8cm). Write on the triangle the value of the height and the value of the base with the units of each. The gradient = height/base, and the units of the gradients are units of height/units of base.

    Where an intercept is required it can either be read directly from the graph, or a suitable calculation may be required.


    Random errors

    Random errors are always present when an experiment is carried out. They can be reduced or minimised but never removed entirely. They are also described as the uncertainty in the measurement. They can be reduced by taking repeat readings. E.g. a measurement of length using a metre ruler can be given as (25.6 ± 0.1)cm. The units must be included.

    Uncertainty in the measurement from a set of results (e.g. a measurement is repeated 8 times to give 8 values for the length) can be found by first calculating the mean. However, this cannot be given to a higher number of significant figures than the original values. Then find the difference between the mean and the furthest away value and ± it.

    E.g. 8 readings of diameter of a wire are measured with a micrometer to the nearest 0.01mm
    0.30, 0.28, 0.29, 0.27, 0.28, 0.26, 0.31

    The values are all different, but not because a mistake has been made. The micrometer is only capable of giving readings to ±0.01mm, so this would be the error even if all readings were the same. There is also a small variation in the diameter of the wire.

    The mean of these values is 0.2825mm, 0.28mm to the correct number of significant figures. The smallest reading is 0.28mm, and the largest is 0.31mm. The differences between these and the mean are 0.02 and 0.03mm, so the diameter is (0.28 ± 0.03)mm.

    Minimum uncertainty – as mentioned above, there is always an uncertainty in each and every measurement and if there is no variation in readings then the uncertainty is the precision of the measuring instrument.


    Percentage uncertainty

    The most accurate reading is the one with the smallest percentage uncertainty. % uncertainty = (actual uncertainty/reading) x 100.


    Systematic errors

    Systematic errors affect all readings by the same amount and are usually “zero errors”, for example:

    Zero errors in meters. This is where the meter doesn’t read zero when disconnected. Corrections can be made by adding or subtracting the required amount. E.g. if an ammeter reads +0.01A, 0.01A must be subtracted from every reading.

    Zero errors in other measuring instruments. This is where the instrument does not read zero even when the reading should obviously be zero. E.g. a micrometer that has been “zeroed” properly should read 0.000 when the jaws are tightened with nothing in between them. If they do not read 0.000, there is a zero error which can be corrected in the same way.
    Thank you so much for this!



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    anyone finished syllabus yet?
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    (Original post by CD223)
    Thank you so much for this!



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    No problem! It's pretty useful having a version with all the rambling and ridiculous exercises cut out anyway.
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    (Original post by Ilovemaths96)
    anyone finished syllabus yet?
    The whole syllabus?My class has just started Raditation and Nuclear Physics(to be fair it doesn't look that hard) the equations are fairly logical from what I've seen.Then my class has to Astrophysics and we are done, of course we have the ISAs to do both AS resits and A2
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    (Original post by Ilovemaths96)
    anyone finished syllabus yet?
    Just got a few more weeks or so of astro and the EMPA left.
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    (Original post by Ilovemaths96)
    anyone finished syllabus yet?
    Nope! Got until Easter to finish mine. You?


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    (Original post by Lau14)
    No problem! It's pretty useful having a version with all the rambling and ridiculous exercises cut out anyway.
    You're telling me! Thank you!

    Got an email back today about my Oxford rejection by the way! Aha.


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    (Original post by CD223)
    You're telling me! Thank you!

    Got an email back today about my Oxford rejection by the way! Aha.


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    Did you get your score back then?
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    (Original post by Lau14)
    Did you get your score back then?
    -> 40/100 on the MAT (193rd out of 582 people)
    -> 3.5/9 in the interviews
    -> 4/9 overall (they usually accept all people with 8 or 9)
    -> There was a 42% increase in CS applications this year. 113 were shortlisted for 37 places. St John's received 30 CS applications and made just 1 offer.

    ...That's the gist of it aha! Seems like I wasn't quite up to it
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    (Original post by CD223)
    -> 40/100 on the MAT (193rd out of 582 people)
    -> 3.5/9 in the interviews
    -> 4/9 overall (they usually accept all people with 8 or 9)
    -> There was a 42% increase in CS applications this year. 113 were shortlisted for 37 places. St John's received 30 CS applications and made just 1 offer.

    ...That's the gist of it aha! Seems like I wasn't quite up to it
    Only made one offer?! and St John's is a pretty big college! But you must have done really well just to be in interviews I really want to ask for my interview scores now again but I don't want to be a pain...
 
 
 
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