OCR Physics A G485 - Frontiers of Physics - 18th June 2015

How many marks could you potentially drop to get an A?

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Nice, same

How many marks could you potentially drop to get an A?

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Was the strong nuclear question attractive or repulsive?

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To be safe 23!

Do you remember how you got there?

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Was the strong nuclear question attractive or repulsive?

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I could scrape it then but I'm just worried about mistakes in longer writing questions and calculations.

Are they relatively generous for ecf marks and if it's a minor error, will you not lose all of the marks?

Sorry about the questioning

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I remember on the tour before the interview someone said they'll probably let you off with one A*. They give offers to 80% of applicants which is quite high compared to other good Unis so it doesn't seem like they're that strict.

Yeah

Power stored in capacitor each time is 0.5CV^2
This is discharged into the resistor equal to I^2R
It discharges over 1 time period (this assumption might be wrong)
Then use P=E/t and equate the top two lines and rearrange for I.

So I got an equation with I^2 being proportional to f, so my logic for the next bit was to say 'I is proportional to root f, so I would increase by a factor of root 2, not 2'.

I'm not sure there were any questions in that exam that required you to use your answer from a previous part ( correct me if im wrong ) - eg if it asked you to calculate the wavelength in part ai) then in part aiii) it asked you to calculate the energy of the wavelegnth. You would get the ECF mark. - But I don't think there was any like this?

For the writting questions I don't think you would get any ECF marks in this paper.
If for instance in that rate of temp thing you x your energy by 0.001 right at the beginning you would ONLY get the method marks. You wouldn't get the Answer mark. - But I'm not an OCR examiner and nor do I know how lenient the mark scheme will be this year, but I do belive that has generally how marks have been awarded in the past.

Ohhh, okay.
I guess that makes sense.

For the increase in temperature, why don't you multiply by 0.01? Isn't it the energy of the x-ray photons?

Ironically, I crossed out the 0.99 one since the change in temperature was too high.
It'd make more sense if the temperature change was only 6℃ initially.

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How do you do the question before that?
The calculation one to calculate current?

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the increase in temp is due to 99% of electrons energy converted to heat 1% is converted to X ray photons.