Question

1. a heat engine operates between two thermal reservoirs at 500 k and 300 k. 1 point what is the maximum theoretical efficiency this engine can achieve? mark only one oval. 83% 60% 40% 67% 22. two identical metal blocks at different temperatures are placed in thermal 1 point contact. which statement best explains what happens to their internal energies? mark only one oval. internal energy is destroyed in the process only the cold block changes internal energy the hot block loses internal energy while the cold block gains internal energy both blocks gain internal energy equally 23. a gas undergoes a cyclic process returning to its initial state. what can you * 1 point conclude about the total change in internal energy for the complete cycle? mark only one oval. it is zero it equals the work done by the gas it depends on the path taken it equals the heat added to the gas

Explanation:

Step1: Recall the formula for the efficiency of a Carnot engine

The efficiency formula for a Carnot engine is $\eta = 1-\frac{T_{c}}{T_{h}}$, where $T_{c}$ is the temperature of the cold reservoir and $T_{h}$ is the temperature of the hot reservoir.

Step2: Substitute the given values into the formula

Given $T_{h}=500\ K$ and $T_{c} = 300\ K$. Then $\eta=1-\frac{300}{500}=1 - 0.6=0.4$.

Step3: Convert the efficiency to a percentage

Multiply the result by 100 to get the percentage. So, $\eta = 0.4\times100\% = 40\%$.

For question 22:

According to the law of conservation of energy and the concept of heat transfer. When two objects are in thermal contact, heat (a form of energy transfer) occurs from the hot object to the cold object. The internal energy of an object is related to its temperature (for ideal cases). The hot block loses internal energy (as it gives out heat) and the cold block gains internal energy (as it absorbs heat).

For question 23:

Internal energy is a state - function. A cyclic process means that the gas returns to its initial state. For a state - function, when the initial and final states are the same, the change in the state - function is zero. So, for a cyclic process of a gas, since it returns to its initial state, the total change in internal energy $\Delta U=0$.

Answer:

1. 40%
2. The hot block loses internal energy while the cold block gains internal energy
3. It is zero