We know the following formula:

$$P=V^2/R.$$

I want to ask **what the $R$ in the above formula represents.** Is it the normal resistance of the resistor (load) or is it the increased resistance of the resistor (load) due to heat generation and consequently, increase in temperature of the resistor (load).

I am asking this because today we solved a question in class which read:

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> The resistance of a 240V and 100W electric lamp heats up from room temperature to operating temperature. As it heats up its resistance is increased by a factor of 16. What is the resistance of the lamp at room temperature?
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The answer to the about problem was $36\:\Omega$ which obviously assumed that the $R$ in the above formula represents the resistance of the bulb when its temperature increases when its operating.

I think the answer should simply be $576 \:\Omega$. I think the $R$ in the formula simply shows what the resistance of the bulb will be when there is no increase in temperature, since it is derived using ohm's law (which works under constant physical conditions).

Please note that this is not a homework question and the teacher is probably not going to discuss it in class again (unless the real answer is not $36\:\Omega$ and I am correct).