11.2.2

Non-Flow Processes

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Isothermal and adiabatic processes

If a gas expands at a constant temperature it is isothermal, if it expands with no heat transfer it is adiabatic.

Illustrative background for IsothermalIllustrative background for Isothermal ?? "content

Isothermal

  • If a gas expands at a constant temperature it is isothermal.
  • An isothermal line on a pressure-volume graph is a curved line of constant temperature.
  • The product of the pressure and the volume is a constant.
    • pV=constantpV=constant
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Adiabatic

  • If a gas expands with no heat transfer it is adiabatic.
  • This means the first law becomes:
    • ΔU=W{\Delta}U= W
  • The condition for an adiabatic expansion is:
    • pVγ=constantpV^{\gamma}= constant
  • Where γ\gamma is a constant.

Constant pressure and volume

Gasses can expand or be compressed under constant pressure or volume.

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Constant pressure

  • At constant pressure, the work done by a gas is given by the pressure multiplied by the change in volume. The equation for work done is:
    • Work done = pressure x change in volume
    • W=pΔVW=p{\Delta}V
  • Work done is measured in Joules.
Illustrative background for Constant volume  Illustrative background for Constant volume   ?? "content

Constant volume

  • If a gas is acted on at a constant volume no work is done as ΔV{\Delta}V = 0.

Jump to other topics

1Measurements & Errors

2Particles & Radiation

3Waves

4Mechanics & Materials

5Electricity

6Further Mechanics & Thermal Physics (A2 only)

7Fields & Their Consequences (A2 only)

8Nuclear Physics (A2 only)

9Option: Astrophysics (A2 only)

10Option: Medical Physics (A2 only)

11Option: Engineering Physics (A2 only)

12Option: Turning Points in Physics (A2 only)

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