# A lightbulb contains Ar gas at a temperature of 295K and at a pressure of 75kPa. The light bulb is switched on, and after 30 minutes its temperature is 418 K. What is a numerical setup for calculating the pressure of the gas inside the light bulb at 418K?

## Assume the volume of the light bulb remains constant.

May 9, 2017

The assumption is quite reasonable.........

#### Explanation:

${P}_{1} / {T}_{1} = {P}_{2} / {T}_{2}$ given constant $n$, and constant $V$, conditions that certainly obtain with a fixed volume light bulb.

And so ${P}_{2} = {P}_{1} / {T}_{1} \times {T}_{2}$

$= \frac{75 \cdot k P a}{295 \cdot \cancel{K}} \times 418 \cdot \cancel{K}$

$\cong 100 \cdot k P a$.

Had the light bulb been sealed at normal pressure during its manufacture, what do you think might occur when it is operated?