Questions about the Physics Practical - May 19th

[iwillrise]

I've been going through some past papers, and since the format is the same every single year, there seems to be a lot we can do to prepare for it. Kinda.

There are things I still don't understand though, even from the mark scheme. Please, someone help a brother out, quickly reply to a few of my questions. Maybe other people might also get some help from your answers. Thanks.

1) When drawing up the table and inserting our values on Q1, do CIE actually put marks on the values we put in. Is there like a range of values which they'll accept? For example, we have to set up our apparatus with six sets of readings, with six sets of "l", then we switch on the power supply and ammeter and record the current at each reading. The current value depends of the value of "l" we used. Will there be any marks on the current value?

2) For the graph question, every year there are 3 marks on the graph, and 1 mark apiece for line of best fit, gradient, and y-intercept. Firstly, the graph itself, after we join the points in a line of best fit, the graph won't be wrong, right? The 3 marks go on the scale used and axes and stuff? So as long as I draw the graph properly, using the values I got earlier, I'll get all 3 marks? Or is there a trend or does the graph actually have to look like the corrector's? Also, is the gradient going to be correct as long as we got it from our graph, or is there a range for that? For the y-intercept, I usually just extend my graph, and see where it cuts the y-axis.

3) For % uncertainty, can someone please give me a rough guideline? I know how to do it, but in the mark schemes they talk about "absolute uncertainty" and have a range for that. What do they meeeeaaaannn?

4) This Q is there every year, and I NEVER get it, what do they want me to write when they ask "JUSTIFY THE NUMBER OF SIGNIFICANT FIGURES USED"????

5) Lastly, is there anything I can memorise for that last question, asking about limitations and improvements, that are likely to be constant throughout the years. i.e= not enough readings....



Thanks in advance for any answers.

 

[Dr Death]

Yes there will be a range. They may give E.C.F
Also you seen to have flipped paper 3 and paper 5 because you don't require error bars in paper 3.
For percentage uncertainty, it is : uncertainty/actual Length x 100
Justify the relationship: (k1-k2)/k1

 

[SebastianM]

1) When drawing up the table and inserting our values on Q1, do CIE actually put marks on the values we put in. Is there like a range of values which they'll accept? For example, we have to set up our apparatus with six sets of readings, with six sets of "l", then we switch on the power supply and ammeter and record the current at each reading. The current value depends of the value of "l" we used. Will there be any marks on the current value?
No. There actually isn't any range as such in the tables. Like, the example you used, you maybe using different values of R, for every reading, so you get different values of I. Other people, however, will choose different values of R, according to their convenience. But for the question on the first page, where the R and V is SAME for everyone and they ask you for the current, then YES, their is a range for that.


2) For the graph question, every year there are 3 marks on the graph, and 1 mark apiece for line of best fit, gradient, and y-intercept. Firstly, the graph itself, after we join the points in a line of best fit, the graph won't be wrong, right? If you have drawn it as a line of best fit, and your scaling is NOT awkward, as in multiples of 3 or such, then your graph is right. Of course, for your graph to be right, your plotted points must be exactly that from the table you drew up!
The 3 marks go on the scale used and axes and stuff? So as long as I draw the graph properly, using the values I got earlier, I'll get all 3 marks? Or is there a trend or does the graph actually have to look like the corrector's? Say your graph doesn't look like anyone's from your class, and your readings in the table are clearly wrong, you will still get your full marks in graph, again, given that you have drawn it from the readings obtained in your table, and you obtained your Y Intercept and Gradient from your graph. You will get those marks as ECF (Error Carried Forward). [CIE only penalizes your mistakes once, if the followup questions' methods are all right, and you are obtaining wrong answers only for the wrong answer obtained above, you will get ECF marks.] Of course you will lose ONE marks from your table, since the values are dead wrong and given that the other things in the table to be right, like the heading/ units etc.
Also, is the gradient going to be correct as long as we got it from our graph, or is there a range for that? For the y-intercept, I usually just extend my graph, and see where it cuts the y-axis.
As I have already mentioned, the gradient has to be correct from your graph.
Yes, you can do that to obtain the Y Intercept as long as you draw the graph from the origin. Or else, you will have to use Y= mX + C to obtain your C.

3) For % uncertainty, can someone please give me a rough guideline? I know how to do it, but in the mark schemes they talk about "absolute uncertainty" and have a range for that. What do they meeeeaaaannn?
Uncertainty/Actual Length x 100
It means the percent you are uncertain of your results. I don't know how to explain this further actually.


4) This Q is there every year, and I NEVER get it, what do they want me to write when they ask "JUSTIFY THE NUMBER OF SIGNIFICANT FIGURES USED"????
It's simple, really. What was the least amount of significant figures you obtained from your readings/ the least specified on the paper? What I mean by that is, say, it is mentioned that it is 6.00 V cell. Then all the answers in that section should be 3- 4 sf. That's your justification.

5) Lastly, is there anything I can memorise for that last question, asking about limitations and improvements, that are likely to be constant throughout the years. i.e= not enough readings....
Sadly, no. That question is the one that baffles most people, and the only way to score is to remember the things that troubled you the most during this experiment. As you do experiment 2, you WILL encounter some things where you just think that this shouldn't be like that, it's not making the results obtained fair. Those are the answers actually.
One of them ALWAYS works, so you can just put it on your paper almost immediately.
LIMITATION It is not enough to take only 2 readings.
IMPROVEMENT Take at least five readings and plot a graph.


I hope to have answered all your questions.

 

[iwillrise]

1) When drawing up the table and inserting our values on Q1, do CIE actually put marks on the values we put in. Is there like a range of values which they'll accept? For example, we have to set up our apparatus with six sets of readings, with six sets of "l", then we switch on the power supply and ammeter and record the current at each reading. The current value depends of the value of "l" we used. Will there be any marks on the current value?
No. There actually isn't any range as such in the tables. Like, the example you used, you maybe using different values of R, for every reading, so you get different values of I. Other people, however, will choose different values of R, according to their convenience. But for the question on the first page, where the R and V is SAME for everyone and they ask you for the current, then YES, their is a range for that.


2) For the graph question, every year there are 3 marks on the graph, and 1 mark apiece for line of best fit, gradient, and y-intercept. Firstly, the graph itself, after we join the points in a line of best fit, the graph won't be wrong, right? If you have drawn it as a line of best fit, and your scaling is NOT awkward, as in multiples of 3 or such, then your graph is right. Of course, for your graph to be right, your plotted points must be exactly that from the table you drew up!
The 3 marks go on the scale used and axes and stuff? So as long as I draw the graph properly, using the values I got earlier, I'll get all 3 marks? Or is there a trend or does the graph actually have to look like the corrector's? Say your graph doesn't look like anyone's from your class, and your readings in the table are clearly wrong, you will still get your full marks in graph, again, given that you have drawn it from the readings obtained in your table, and you obtained your Y Intercept and Gradient from your graph. You will get those marks as ECF (Error Carried Forward). [CIE only penalizes your mistakes once, if the followup questions' methods are all right, and you are obtaining wrong answers only for the wrong answer obtained above, you will get ECF marks.] Of course you will lose ONE marks from your table, since the values are dead wrong and given that the other things in the table to be right, like the heading/ units etc.
Also, is the gradient going to be correct as long as we got it from our graph, or is there a range for that? For the y-intercept, I usually just extend my graph, and see where it cuts the y-axis.
As I have already mentioned, the gradient has to be correct from your graph.
Yes, you can do that to obtain the Y Intercept as long as you draw the graph from the origin. Or else, you will have to use Y= mX + C to obtain your C.

3) For % uncertainty, can someone please give me a rough guideline? I know how to do it, but in the mark schemes they talk about "absolute uncertainty" and have a range for that. What do they meeeeaaaannn?
Uncertainty/Actual Length x 100
It means the percent you are uncertain of your results. I don't know how to explain this further actually.


4) This Q is there every year, and I NEVER get it, what do they want me to write when they ask "JUSTIFY THE NUMBER OF SIGNIFICANT FIGURES USED"????
It's simple, really. What was the least amount of significant figures you obtained from your readings/ the least specified on the paper? What I mean by that is, say, it is mentioned that it is 6.00 V cell. Then all the answers in that section should be 3- 4 sf. That's your justification.

5) Lastly, is there anything I can memorise for that last question, asking about limitations and improvements, that are likely to be constant throughout the years. i.e= not enough readings....
Sadly, no. That question is the one that baffles most people, and the only way to score is to remember the things that troubled you the most during this experiment. As you do experiment 2, you WILL encounter some things where you just think that this shouldn't be like that, it's not making the results obtained fair. Those are the answers actually.
One of them ALWAYS works, so you can just put it on your paper almost immediately.
LIMITATION It is not enough to take only 2 readings.
IMPROVEMENT Take at least five readings and plot a graph.


I hope to have answered all your questions.

Thanks so much man, a huge help, couldn't have asked for anything better!!!!