Which term defines the amount of mechanical work an engine can do per unit of heat energy it uses? A. specific heat B. conductiv
1 answer:
Answer:
Efficiency
Explanation:
- The amount of mechanical work an engine can do per unit of heat energy it uses is called its efficiency.
- It is also defined as the output divided by the total electrical power consumed.
- In terms of heat, efficiency of engine is given by :
are output heat and input heat respectively.
Hence, the correct option is (d) "efficiency"
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Answer:
Qt = 940500 [J]
Explanation:
In order to solve this problem and understand it well, we must analyze that the ice melts or changes phase at a temperature of 0 [°c], then the water at a temperature of 100 [°C] evaporates or changes phase. That is, we have 5 different stages of water (initially in the form of ice), which are:
-) From -30 [°C] to 0 [°C] = Sensible change of temperature
-) At 0 [°C] = Latent heat of melting ice = 334 x 10³ [J/kg]
-) From 0 [°C] to 100 [°C] = Sensible change of temperature
-) At 100 [°C] = Latent heat of fusion for water = 2260 x 10³ [J/kg]
-) From 100 [°C] to 130 [°C] = Sensible change of temperature (superheating)
We can calculate the sensible heat of any process with the following expression:
where:
Q = heat or thermal energy [J]
m = mass of the body or substance = 300 [g]
Cpw = specific heat of the water = 4180 [J/kg*°C]
Cpi = specific heat of the ice = 2090 [J/kg*°C]
Tfinal = final temperature of the process [°C]
Tinicial = initial temperature of the process [°C]
And for some latent heat process, we can calculate the thermal energy using the following expression:
where:
Dhfus/eva = Fusion heat or latent heat [J/kg]
So, we need to calculate the fice processes.
And the final step is the sum of all the five heat processes.