**What is the maximum efficiency of an engine?** Modern gasoline engines have a maximum thermal efficiency of **more than 50%**, but road legal cars are only about 20% to 35% when used to power a car.

**What is the efficiency of heat engine *?** The efficiencies of various heat engines are as follows: It is just **3%** efficient for ocean thermal energy conservation. Automotive gasoline engines are nearly 25% efficient. Similarly, coal-fired power stations have 49% efficiency.

**What is the maximum percent efficiency of a heat engine operating between these temperatures?** The maximum efficiency called the carnot efficiency for heat engine operating between reservoirs at different temperatures is **1 minus the cold temperature divided by the hot temperature** and expressed in Kelvin.

**When would a heat engine have 100% efficiency?** A heat engine is considered to be 100% efficient **if only all the heat is converted into useful work or mechanical energy**. Since heat engines cannot convert all the heat energy into mechanical energy, their efficiency can never be 100%.

## What is the maximum efficiency of an engine? – Additional Questions

### Why is efficiency always less than 100%?

The percentage of the work input that becomes work output is the efficiency of a machine. **Because there is always some friction**, the efficiency of any machine is always less than 100 percent.

### Is there any device with 100% efficiency?

**No,Efficiency of a machine is always less than 100%** as output energy is always less than the input energy, because some energy is lost to overcome friction.

### Can a Carnot heat engine attain 100% efficiency justify your answer?

**Even Carnot engine cannot give 100% efficiency** because. In order to achieve 100% efficiency (η=1), Q2 must be equal to 0 which means that all the heat form the source is converted to work. The temperature of sink means a negative temperature on the absolute scale at which the temperature is greater than unity.

### Why is the efficiency of Carnot cycle not 100%?

The efficiency is 100% only when T_{2} is zero or T_{1} is infinite. This is not possible since **some amount of heat gets rejected to the sink**.

### What factors affect the efficiency of a real heat engine?

The loss of energy due to the **friction, viscosity and insufficient combustion** will reduce the efficiency of a heat engine from its ideal value.

### How can you increase the efficiency of a heat engine?

Therefore, the efficiency of the heat engine can be increased by **decreasing the temperature of the cold sink or increasing the temperature of the hot source**.

### What is an ideal heat engine?

The idea of an ideal heat engine was first developed by Sadi Carnot in 1824. He imagined a heat engine which was **free of friction and the working substance undergoes a completely reversible cycle consisting of two isothermal and two adiabatic changes**.

### How do you calculate heat efficiency?

**efficiency =WQH=1−TCTH**. These temperatures are of course in degrees Kelvin, so for example the efficiency of a Carnot engine having a hot reservoir of boiling water and a cold reservoir ice cold water will be 1−(273/373)=0.27, just over a quarter of the heat energy is transformed into useful work.

### How do you calculate the maximum efficiency of an engine?

Solution : **Efficiency `=(T_(2)-T_(1))/(T_(2))`** <br> `T_(2)=100+273=373K` <br> `T_(1)=25+273=298K` <br> Efficiency `=(373-298)/(373)` <br> `=(75)/(373)=0.20=20%`. Step by step solution by experts to help you in doubt clearance & scoring excellent marks in exams.

### What is the efficiency formula?

Efficiency can be expressed as a ratio by using the following formula: **Output ÷ Input**. Output, or work output, is the total amount of useful work completed without accounting for any waste and spoilage. You can also express efficiency as a percentage by multiplying the ratio by 100.

### What is the efficiency of Carnot engine?

The efficiency of carnot’s engine is **50%**.