An atmospheric research probe descending through the dense upper atmosphere of a gas giant captures a sample of gas to analyze.
Explain what is meant by an adiabatic process, and state the practical condition required for a real physical process to be approximated as adiabatic.
During the intake and compression phase, the gas sample is compressed adiabatically in a sampling cylinder from an initial pressure of 4.5×105 Pa4.5 \times 10^5 \text{ Pa}4.5×105 Pa and volume V1V_1V1 to a final pressure of 1.8×107 Pa1.8 \times 10^7 \text{ Pa}1.8×107 Pa and volume V2V_2V2. Taking the adiabatic index γ\gammaγ for this gas mixture to be 1.31.31.3, calculate the compression ratio V1V2\frac{V_1}{V_2}V2V1 of the cylinder.
The probe utilizes a small reciprocating auxiliary power unit. Explain why a spark-ignition engine cycle is restricted to a much lower compression ratio than a compression-ignition (diesel) engine cycle.
