Energy, temperatures and efficiency

In summary, The conversation is about a student who is working through a past paper for an exam and is having trouble with a question about the efficiency of a steam engine. They ask for help on what equation to use and someone suggests checking Wikipedia for the Carnot efficiency formula, which only depends on the temperatures of the hot and cold reservoirs. The student thanks them for the helpful response.
  • #1
Flucky
95
1
Hi all

Working through a past paper as I have an exam tomorrow and can't quite see where to start with the following question.

Homework Statement



A steam engine produces 2.4 kJ of work per cycle for a heat input of 6 kJ. If the temperature of the hot source for the engine is 600 °C and the temperature of the cold sink is 100°C, what is the maximum possible efficiency of the engine?

Homework Equations



The only equations I can think of relating to this question involve other variables that aren't given. My initial thought was that as we're finding the efficiency any unknown values will cancel each other out, but I don't seem to get anywhere.

Could somebody please point me in the direction of what equation I should be looking at?

The annoying thing is it's only a 2 mark question!

Thanks in advance.
 
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  • #2
They are asking for the maximum efficiency, for a heat engine, this is also called the Carnot efficiency. This efficiency can be expressed with what you are given. Check wikipedia for the formula (it only depends on the temperatures of the hot and cold reservoirs) :) .
 
  • #3
rock.freak667 said:
They are asking for the maximum efficiency, for a heat engine, this is also called the Carnot efficiency. This efficiency can be expressed with what you are given. Check wikipedia for the formula (it only depends on the temperatures of the hot and cold reservoirs) :) .

Thanks a lot for that. I guess I missed the lecture on it :p

Thanks for replying as well.
 

1. What is energy and how is it measured?

Energy is the ability to do work or cause change. It can be measured in joules (J) or calories (cal). A joule is the amount of energy needed to apply a force of one newton through a distance of one meter. A calorie is the amount of energy needed to raise the temperature of one gram of water by one degree Celsius.

2. What is the difference between potential and kinetic energy?

Potential energy is the energy an object has due to its position or condition, such as a stretched spring or a raised object. Kinetic energy is the energy an object has due to its motion, such as a moving car or a spinning top. Both types of energy are measured in joules.

3. How does temperature affect energy?

Temperature is a measure of the average kinetic energy of the particles in a substance. When the temperature increases, the particles move faster and have more energy. This can lead to changes in the state of matter, such as melting or boiling, as well as changes in chemical reactions.

4. What is thermal efficiency?

Thermal efficiency is a measure of how much of the energy input into a system is converted into useful work output. It is calculated by dividing the amount of useful energy output by the total amount of energy input. For example, an engine with a thermal efficiency of 25% means that 25% of the energy from the fuel is converted into useful work, while the remaining 75% is lost as waste heat.

5. How can we increase energy efficiency?

There are several ways to increase energy efficiency, including using energy-saving appliances, insulating buildings to reduce heat loss, and using renewable energy sources. Also, reducing energy consumption by being mindful of energy use and turning off devices when not in use can greatly improve efficiency. Additionally, implementing more efficient technology and practices in industries can also help to increase overall energy efficiency.

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