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# P=V^2/R and V=IR watch

1. So i did a past paper question and it said:
The mains bulb is marked 40W, 230V
a) show that the current in the mains bulb is about 0.2A when it is operating normally. I did this using P=VI, nice and easy.
b)Calculate the resistance of the mains bulb when it is operating normally.
Part b also seemed like an easy question but using V^2/P =R and V/I =R give different answers, i think i may be missing something stupid and important, any ideas ?
2. Dont worry was being silly -_-

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Updated: May 31, 2016
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