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Physics Paper 5 tips

afoo.666

afoo.666

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Soldier313 said:
If for example the two variables we're dealing with are VOltage and Current, and the errors provided are for say current, then on plotting, if we place current on the y-axis, the error bars will be vertical, and if we place current on the x-axis, then the error bars will be horizontal
The length of the error bars depends on the scale of the graph as well as the magnitude of the error itself
Click to expand...

thankyou.
what about the magnitude of error ?
 
Soldier313

Soldier313

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afoo.666 said:
why 1.5?
i thought 0.5 above 2.5 and 0.5 below 2.5.
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The value of current was 2A, and the error is plus/minus 0.5
so, you add 0.5 to 2 , to get the upper limit of the error bar, and you subtract 0.5 to get the lower limit of the error bar
hence, 2+0.5 = 2.5 (upper limit) and 2 - 0.5 = 1.5 (lower limit)
 
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Azfar94

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plz tell me how to know the appropriate number of s.f and d.p for filling up the table in question 2?
 
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Azfar94

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plz tell me how to know the appropriate number of s.f and d.p for filling up the table in question 2?
 
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MLSW1994

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Hi, so what are the basic strategies to score full marks for question 1?

This is what I've got in mind so far:
- 3 variables (independent, dependent, constant)
- Draw and label a diagram
- Method for carrying out the experiment (briefly explain how the experiment is carried out, vary the independent variables, record the data, plot a graph)
- Draw a graph and label it (if an equation is given use it to find the x/y axis and the y-intercept and outline how the gradient is calculated)
- Describe at least 5 safety precautions/additional information

Anything else to add on? o_O
 
Ramsha007

Ramsha007

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fb.junks said:
1.33-1.28 is this case specifically
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I am getting 1.28 for best and 1.20 for worst.It can be possible right:unsure: is it necessary that if u are getting worst gradient value bigger than i should get that too in the same ques or they can be different ???:oops:
 
Ramsha007

Ramsha007

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fb.junks said:
Paper 5 Tips: Practical Test
Planning Question
• Do not panic if the context of the question appears unfamiliar to you. During your A Level studies you will have used or learnt about suitable apparatus for completing the task. If you are asked to ‘use’ any unfamiliar apparatus the question will supply you with all the details that you need to know about.
• Read the question very carefully – it may give you guidance on those aspects of your plan to which you need to pay particular attention. It will also help you to identify the independent and the dependent variables.
• When writing your answer you will need to consider some or all of the following:
- what apparatus you will use
- what experimental arrangement will be used
- what procedure will be followed
- the independent and dependent variables
- the means of keeping other variables constant - use the word ‘constant’
when identifying these variables, saying you will ‘control’ them is insufficient
- how the raw data readings will be processed to give the desired result, e.g. what derived quantities you might calculate or what graph you might plot
- what relevant safety precautions should be in place
• The relationship to be tested, given to you in the introduction to the task, will
suggest the type of graph to be expected. You will need to describe it as
precisely as possible. For example, is it linear, does it pass through the origin? If
you choose a logarithmic graph, you will be expected to predict its slope from the
given expression.
• When writing your answer you must write down all the information clearly and
explicitly - the examiner cannot give you marks for things that are vaguely implied.
• Many of the marks can often be scored by having a good working diagram (even if the accompanying explanation is weak) and so you should spend time making sure that your diagram shows all the relevant details and is fully labelled. For example, make clear the exact points, between which, measurements, such as distance, are to be made.
• The equipment and procedures that you describe in your answer should be realistic and workable.
• One mark is available for describing safe working. This must relate specifically to the apparatus being used. It is not sufficient to write, for example, ‘keep all bags and coats out of the way’.
• Additional marks are available for detailed descriptions of apparatus/techniques. There are always more possible answers than marks available, so if you write your plan carefully, then some these marks should be gained as you go along. It is not expected that you write a separate section solely for the detail marks.
• As part of your preparation for this question you should plan some of your own experiments, but this should be done under the close supervision of your teacher. Also practise answering past papers.
• A sketch graph is not necessary, but if drawn it should be consistent with your description of the graph.

Evaluating data Question
• The number of significant figures used in a derived quantity that you calculate from your raw readings should be equal in number to (or possibly one more than) the number of significant figures in the raw readings. For example, if you measure potential difference and current to 2 and 3 sig figs respectively, then the corresponding value of resistance calculated from them should be given to 2 or 3 sig figs, but not 1 or 4. If both were measured to 3 significant figures, then the resistance could be given to 3 (or 4) sig figs.
• When drawing your graph, do not forget to label each axis with the appropriate quantity and unit, using the same format for expressing column headings in a table. Choose a scale such that the plotted points occupy at least half the graph grid in both the x and y directions. The x-axis scale should increase positively to the right and the y-axis scale should increase positively upwards. Use a convenient scale such as 1, 2 or 5 units to a 2cm square as you will then be less likely to make a mistake with the position of your plotted points and it will be easier for you to read off points from your graph if you are calculating the gradient or finding an intercept. Similarly, it is good practice to mark values on at least every other 2cm square.
• All your plotted points should be on the grid; points in the white margin area will be ignored. Plot all your observations and ensure that they are accurate to half a small square. A fine cross (or an encircled dot) drawn with a sharp pencil is acceptable, but be careful not to obscure the position of your points by your line of best fit or other working.
• When drawing your line of best fit, ensure you have an even balance of points about the line along its whole length. If it is a straight line, use a clear plastic rule so that you can see points on both sides of the line as it is being drawn.
• Show all your working when calculating a gradient. It is helpful to draw the triangle used to calculate the gradient on the graph and to clearly label the coordinates of the vertices (accurate to half a small square). These values can then be used in the gradient calculation. The length of the hypotenuse of the triangle should be greater than half the length of the graph line.
• If you are required to give a value for the y-intercept, it may be possible to directly read it off from your graph from an axis where x=0. If this is not possible you can instead calculate the y-intercept by using the equation of a straight line. In this case you should substitute into this equation a pair of x and y values from your line of best fit along with your calculated value of gradient.
• It is particularly important that the rules, previously given for significant figures, are strictly adhered to.
• You will be expected to use the uncertainty given in the raw data to find the uncertainty in calculated data. The latter will involve a function such as a logarithm. This requires plenty of practise, if you are to be able do it with confidence in the examination.
• You will need to be able to translate the calculated uncertainties into error bars on your graph and then to draw the worst acceptable line. Again, this requires plenty of practise.
• Once the graph has been drawn, you will be expected to find uncertainties in both the gradient and the intercept – using your line of best fit and your worst acceptable line. A lot of marks depend on your being able to calculate the uncertainties in the calculated data.
• Every candidate is provided with the same data and so the final values calculated should be very similar. One mark is available to candidates who manage to work within a given tolerance, determined by the Principal Examiner.

Source:Learner Guide for Cambridge AS and A Level Physics(© Cambridge International Examinations 2012)

Hope this helps!!!:)
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u said we can use y intercept directly if x=0, what will be the shape of graph when we have to find y- intercept by sustituting the values in the eq? As far as i know y- intercept is the point where the line join y-axis so isn't the x going to be zero all the time.May be a stupid ques but would be glad if u can ans:)
 
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fb.junks

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Ramsha007 said:
u said we can use y intercept directly if x=0, what will be the shape of graph when we have to find y- intercept by sustituting the values in the eq? As far as i know y- intercept is the point where the line join y-axis so isn't the x going to be zero all the time.May be a stupid ques but would be glad if u can ans:)
Click to expand...
When u have a graph with no false origin u can directly tell the y-intercept when the graph line cuts the y-axis.
Now for the equation part if u have a false origin.U take a point of the graph(x,y) and put in equation.y=mx+c.
U are correct that when x is zero the value of y is the y-intercept but in this case u dont have that point on the graph(the y because of false origin) so u use the equation for this.

No question is a stupid question.Everybody is learning here :)
 
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fb.junks

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Ramsha007 said:
I am getting 1.28 for best and 1.20 for worst.It can be possible right:unsure: is it necessary that if u are getting worst gradient value bigger than i should get that too in the same ques or they can be different ???:oops:
Click to expand...
U might have made a little with the worst acceptable line because values are given in the question so answer should be similar of all the candidates.
 
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backtodev

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Hi - does anyone know what the diagram in Nov 2007 should look like?
Plus what's the range for an ammeter?
Oh and what's the difference between using a vernier caliper and a micrometer screw gauge?
 
Ramsha007

Ramsha007

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fb.junks said:
When u have a graph with no false origin u can directly tell the y-intercept when the graph line cuts the y-axis.
Now for the equation part if u have a false origin.U take a point of the graph(x,y) and put in equation.y=mx+c.
U are correct that when x is zero the value of y is the y-intercept but in this case u dont have that point on the graph(the y because of false origin) so u use the equation for this.

No question is a stupid question.Everybody is learning here :)
Click to expand...


Thanks a ton!!!!!
 
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