You may be someone who scratches their head when it comes to working on a car engine... maybe not. But, at least you can say now that you have a general understanding of The First Law of Thermodynamics and how it applies to an engine. Make sure you have a good conceptual understanding of the concepts in this lesson using the multiple-choice activity below.
As a balloon rises, it transfers 18 J of heat to the surrounding air as the gas expands and does 12 J of work on the air. What is the balloon's change in internal energy?
- -6 J
- 6 J
- -30 J
- 30 J
Q is negative when heat is lost by the system (or the surroundings gain it). W is positive when the system does work on the environment.
Q is negative when heat is lost by the system (or the surroundings gain it). W is positive when the system does work on the environment.
Q is negative when heat is lost by the system (or the surroundings gain it). W is positive when the system does work on the environment.
Q is negative when heat is lost by the system (or the surroundings gain it). W is positive when the system does work on the environment.
Which of the following would be the appropritate First Law equation for an isothermal process?
- \(\mathsf{ \Delta U = - W}\)
- \(\mathsf{ \Delta U = Q }\)
- \(\mathsf{ Q = W}\)
In an isothermal process, there is no change in the internal energy, so \(\small\mathsf{ \Delta U = 0 }\).
In an isothermal process, there is no change in the internal energy, so \(\small\mathsf{ \Delta U = 0 }\).
In an isothermal process, there is no change in the internal energy, so \(\small\mathsf{ \Delta U = 0 }\).
A gas refrigerant is compressed by 143 J of work. The internal energy of the gas increased by 104 J. How much energy has been transferred to heat?
- 39 J
- -39 J
- 247 J
- -247 J
The internal energy was increased. The work was done on the gas, so the work value is negative.
The internal energy was increased. The work was done on the gas, so the work value is negative.
The internal energy was increased. The work was done on the gas, so the work value is negative.
The internal energy was increased. The work was done on the gas, so the work value is negative.
Which of the following best describes a cyclic thermodynamic process?
- No heat or work is done on or by the system.
- Only work is done by the system, no heat is exchanged with the environment.
- Only heat is exchanged with the environment, no work is done with the environment.
- Heat and work can be exchanged, but the system's condition returns to its original condition after that echange.
In a cyclic process, the system's internal energy starts and ends at the same amount.
In a cyclic process, the system's internal energy starts and ends at the same amount.
In a cyclic process, the system's internal energy starts and ends at the same amount.
In a cyclic process, the system's internal energy starts and ends at the same amount.
Which process is reflected in the First Law equation \(\small\mathsf{ \Delta U = - W}\)?
- isvolumetric
- isothermal
- adiabatic
- cyclic
Think about which process has no change in internal energy, but work and heat can be exchanged with the surroundings.
Think about which process has no change in internal energy, but work and heat can be exchanged with the surroundings.
Think about which process has no change in internal energy, but work and heat can be exchanged with the surroundings.
Think about which process has no change in internal energy, but work and heat can be exchanged with the surroundings.
Summary
Questions answered correctly:
Questions answered incorrectly:
