# Pressure of a lightbulb

## Homework Statement

Suppose a gas-filled incandescent light bulb is manufactured so that the gas inside the bulb is at atmospheric pressure when the bulb has a temperature of 20.0 °C. Find the gauge pressure inside such a bulb when it is hot, assuming its average hot temperature is 65.0 °C.

## Homework Equations

(p/t)=(p'/t') where the left hand side is initial pressure and temperature, the right is the when hot.

t= 293.15 K
t'=338.15 K

the gas inside is at atmospheric pressure.

## The Attempt at a Solution

1atm= 1.013x^5 Pa[/B]

i use the formula above, and solve for p'

p' = (pt')/t

p'=(1.013x10^5)(338.15)/(293.15) (Pa*K)/(K) (the right stuff are the units of measurement used)

116850.0597 Pa.

However, I am not getting the answer. I never took a chemistry class, so I am unsure what the difference between gauge pressure/ atmospheric/ absolute pressure is and how to convert it.

I believe my formula is correct but I am not using the correct pressure values.