Paper 4 Thermal Physics B Drills

Q1 Boyle law test

A student records the absolute pressure $p$ for different gas volumes $V$ while keeping the gas at constant temperature.

$V/\mathrm{c}{\mathrm{m}}^3$	30.0	35.0	40.0	50.0	60.0	75.0
$p/\mathrm{kPa}$	203.2	174.3	153.1	123.0	103.2	82.9

1. Calculate $1/V$ for each reading. [1]
2. Plot $p$ against $1/V$ and draw a best-fit straight line. [5]

3. Use the gradient to determine the experimental value of $pV$. [2]
4. Use the intercept to estimate the pressure-sensor offset. [2]
5. State two precautions needed to maintain constant gas temperature. [2]
6. Explain why the volume of gas in connecting tubing should be included. [1]

Q2 First-law p-V data

A gas cycle is plotted on a p-V diagram.

1. State how net work by the gas in one cycle is found. [1]
2. Explain why $\Delta U=0$ over one complete cycle. [2]
3. State how net heat input compares with net work output over a cycle. [2]