Physics - Please HelP! Watch

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#1
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#1
Hi,
I am trying to find the answer for the following questions:
(THEY ARE FROM OCR SALTERS DOUBLE AWARD SCI, SPECIMEN PAPER 2 2003)


(RESISTOR IS 1000ohms)


1)What is the voltage across a 1000 ohm resistor when voltage=0.6v?

2)Calculate the resistance of component X.
(v=8.4)

3)Calculate the power of component X when the output to the transistor is 0.6v

I have looked on BiteSize and it has given me stupid answers!
Please, somebody help!!!!!!!!!
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#2
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I have found the answers on the OCR website.

I need to know how you work them out.

Its Q10 on:
http://www.ocr.org.uk/OCR/WebSite/Da...Z90XRGl82n.pdf

THANKS FOR YOUR HELP!
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mrmarsupial
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V = I/R R=V/I I=V/R


Voltage=Current /Resistance
Resistance=Voltage/Current
Current=Voltage/Resistance



Make sure all units in SI form, Volts Amps and Ohms not MegaOhms or MegaAmps etc
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mrmarsupial
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Didnt read the question sorry, its easy its just 9V - 0.6V = 8.4V

If the current is .0084 amps, the question is asking u to show how u work this out


thats just 8.4V/1000ohms = .0084A


and for the last bit, you know the total current in the circuit is .0084 A(series circuit so its same all way through).

You know the total voltage is 9 volts therefore Resistance = Volt/Current = 9/.0084 = 1071.43 Ohms

Minus 1000 ohms (the fixed resister) from this value

You get component X = 71.43 Ohms
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Hi,
Thanks for the help!

Do you know how to calculate power?

I have the exam tommorow, you help will be highly appreciated!

THANKS!
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mrmarsupial
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Power = Voltage x Current


so voltage is 0.6, current is 0.0084

Power=0.6 x 0.0084

Power = 0.005 Watts
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mrmarsupial
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#7
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Out of interest is the hardest kinda physics question you get on the GCSE higher papers cause its the easiest you get on the AS lvl ones
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