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Formative assessment questions for teaching physics

A2L Item 112

  • Description: Indicate the sign of the work done on a gas during an isobaric compression process.
  • Goal: Hone the concept of work on a gas
  • Source: UMPERG-ctqpe220
  • Keywords: Graphing, Thermodynamics, Work

The question for students:

Item112_fig1.gif

One mole of an ideal monatomic gas is taken around the cycle shown.

The work done on the system during the process B to C is

  1. Positive
  2. Negative
  3. No work is done on the system
  4. Cannot be determined

Commentary for teachers:

Answer

(1) Positive work is done ON the system. Since the path on a V-T diagram is a straight line, the process is isobaric.