This discussion is now closed.

Check out other Related discussions

Official Edexcel AS/A2 Physics Thread

Reply 180

fusionskd

OP

10

.A.

how about oscilloscope used for hall voltage. ?

Never heard of that to be honest, care to elaborate?

Reply 181

fusionskd

OP

10

Arsenal4life

this site is really handy =)..ill be thinking of you all when i open up that exam paper and see none of the hints were correct :P

How sweet of you :p:

lol...

Reply 182

fn137

11

hey one question
in june 2002 paper, planning question

I=k(cosO)n 'n' power ok

so we should be using 'log' here right? but in the marking scheme its written 'ln'

how is it? ln is used when quantities r decreasing exponentially ,but here its not , so y r we using ln then???

HOW DO WE KNOW WHEN TO USE LOG AND WHEN TO USE ln?

Reply 183

Arsenal4life

lol i know its been explained before
but can anybody give me an idiot proof guide of why and how you calibrate a hall probe
o i hate physics cant wait till maths tho

Reply 184

fusionskd

OP

10

njds13

hey one question
in june 2002 paper, planning question

I=k(cosO)n 'n' power ok

so we should be using 'log' here right? but in the marking scheme its written 'ln'

how is it? ln is used when quantities r decreasing exponentially ,but here its not , so y r we using ln then???

HOW DO WE KNOW WHEN TO USE LOG AND WHEN TO USE ln?

It doesnt matter whether you use ln or log to be honest because most markscheme's would have put both in their results, if they've just used ln, then using log would gain you the marks too, dont worry.

ln x = log x/log e
log x = ln x/ln 10

I=k(cos0)^n

ln I = ln k(cos0)^n

ln I = ln k + nln(cos0)

The bases are irrelavent because they are just constants. Ln x is just log base e, where as log x is conventially known as log base 10.

Something like log base 9 for example is = log x/log 9

Reply 185

Kalashnikov

2

Remember this. You can ALWAYS use ln.

Only use log on equations that don't have an "e". If it does have an e, use ln.

It's best to always use ln, which is what I do.

Reply 186

MOBA X

njds13

hey one question
in june 2002 paper, planning question

I=k(cosO)n 'n' power ok

so we should be using 'log' here right? but in the marking scheme its written 'ln'

how is it? ln is used when quantities r decreasing exponentially ,but here its not , so y r we using ln then???

HOW DO WE KNOW WHEN TO USE LOG AND WHEN TO USE ln?

I don't think it really matters, ln is a log to base e so your answer should not be affected, your straigth line graph may look a little different but any gardientr or intercept you get should be the same wether you use ln or log to base 10, personally i would use ln

Reply 187

sphixter

About the capacitors question, what do you guys think might come? The only possible question that I think could come is to time the charging of a capacitor, plot the graph of current against time and divide the area under the graph with the voltage to find the capacitance. That being said how can we accurately time the fall in current. Do we start timing as soon as we complete the circuit and until we reach the appropriate value and then stop? Is there a more accurate method?

Reply 188

gorilla_baby

9

yes, you time it for a set period of time, but i think you recharge it, then redo the whole thing and find an average value

Reply 189

Bertus3223

Guys could really do with some urgent URGENT help, how is a wire forced to oscillate between two magnadur magnets? Would appreciate the help sooooooo much, cheers

Reply 190

FrostMourne.VIII

yeah thanks gorilla for checking, infact they are meant to be that way, one of my old friend is half way across the world and still has the same time and that what the teacher said ..BUT :P a friend of mine refuses to believe that and says its all a conspiracy! loL, had me laughing coz its crazy enough to be true...BUT :P now i have literal/physical proof against him , HA!

Arsenal4life

this site is really handy =)..ill be thinking of you all when i open up that exam paper and see none of the hints were correct :P

+1/WIN.

Reply 191

sphixter

MOBA X

You can answer such questions in two ways, firstly you can calculate the accepted margin of error based on your experimental uncertainty as you have said.secondly you could calculate the percentage difference between your experimental value and the accepted value given in the question, if this percentage difference is less than your experimental uncertainty then the values obviously correspond otherwise they do not.

And by margin of error, you mean percentage error, right? Because I dont see how we can compare a numerical error with a percentage error. Also when we multiply or divide two measurements, we add the percentage error right? And the subsequent error is still in percent?

It just struck me that I said error 6 times in less than 4 lines. :tsr2:

Reply 192

ossie007

rite im def sure Q on how 2 calibrate a hall probe is cumin up
it would beenfit us all if ne1 nos xacly how 2 calibrate 1 lol
cheers

Reply 193

lilpaki

continuing with the log/ln thing, how are the units affected. whats the best way to write the units?

example:

time period t/secounds
flux density B/Tesla

how do the above change once theyve been 'ln'