"The Efficiency of Heat Engines" Utilization of Internal Energy PPT Download

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"The Efficiency of Heat Engines" Utilization of Internal Energy PPT Download

Part One: Guidance Design

Learning point 1: Calorific value of fuel

Message 1: In modern society, most of the energy used by humans is still obtained from the combustion of fuel. There are many types of fuel. Solid fuels include wood, coal, etc., liquid fuels include gasoline, diesel, etc., and gaseous fuels include coal gas, natural gas, etc.

Information 2: When different fuels of the same mass are completely burned, the heat released is different. For example, the heat released by burning 1 kg of coal is more than twice the heat released by burning 1 kg of firewood.

Information 3: The heat released by the complete combustion of 1 kg of a certain fuel is numerically equal to the calorific value of the fuel.

think:

Question 1: How is energy converted during fuel combustion?

answer:____________________________________________.

Question 2: What is the calorific value used to represent?

answer:____________________________________________.

Learning point 2: The efficiency of heat engines

Legend: Figure 14-2-3 shows the energy flow diagram of an internal combustion engine.

think:

Question: What aspects of energy are lost during the operation of a heat engine?

answer:______________________________________________.

PPT on the efficiency of heat engines, part 2: summary of common exams

Type 1 The concept of calorific value

Typical Example 1 Regarding the concept of calorific value, which of the following statements is correct ()

A. The more complete the fuel is burned, the greater its calorific value

B． The fuel is not burned and its calorific value is zero

C. The more heat a fuel releases when burning, the greater its calorific value

D. The calorific value of fuel has nothing to do with the quality and combustion conditions of the fuel

[Commentary by Famous Teachers]The calorific value is a characteristic of the fuel itself. It is only related to the type of fuel and has nothing to do with the shape, quality, volume, or complete combustion of the fuel.

Type 2: Discrimination between power and efficiency

Typical Example 2 Two motorcycles of different brands, A and B, drove the same distance on the same road under the same load. Motorcycle A consumed 300 g of gasoline, and motorcycle B consumed 310 g of gasoline. ,but()

A. The power of motorcycle A is less than the power of motorcycle B

B． The efficiency of motorcycle A is greater than the efficiency of motorcycle B

C. The power of motorcycle A is greater than the power of motorcycle B

D. The efficiency of motorcycle A is less than the efficiency of motorcycle B

[Commentary by Famous Teachers]Power is a physical quantity that indicates how quickly an object does work, while efficiency is the ratio of the part of energy used to do useful work to the energy released by complete combustion of the fuel, which reflects the issue of energy utilization.

Type 3 Related calculations of thermal efficiency

Typical example 3: A middle school supplies boiling water to students. It uses a boiler to heat 200 kg of water from 25 ℃ to 100 ℃, and burns 6 kg of smokeless water.

coal. Try to find: [The specific heat capacity of water is 4.2×103J/(kg·℃), and the calorific value of anthracite is 3.4×107 J/kg]

(1) The heat absorbed by 200 kg of water in the boiler.

(2) The heat released by the complete combustion of 6 kg anthracite.

(3) The efficiency of this boiler.

PPT on the efficiency of heat engines, part 3: classroom feedback

1. The ratio of the heat released when a certain fuel _________ is burned to its mass is called the calorific value of the fuel. The calorific value of gasoline is 4.6×107 J/kg. Its physical meaning is that when gasoline is completely burned _________, the heat released is ______________.

2. Which of the following statements about calorific value is correct ( )

A. The more complete the fuel is burned, the greater the calorific value

B． The complete combustion of 2 kg of coal has a greater calorific value than the complete combustion of 1 kg of coal.

C. When 1 kg of coal is burned, it releases 3×105 J of heat, so the calorific value of coal is 3×105 J/kg.

D. The calorific value is a characteristic of fuel and has nothing to do with the quality of the fuel. Different substances generally have different calorific values.

[Analysis]The ratio of the heat released by complete combustion of a certain fuel to its mass is called the calorific value of the fuel. Calorific value is a characteristic of fuel. It is only related to the type of fuel and has nothing to do with the quality of the fuel or the degree of combustion.

3. When fuel is burned, the ratio of the energy used to do _________work to the heat released by the fuel___________ is called the efficiency of the heat engine.

4. Figure 5-1 is the energy flow diagram of the internal combustion engine. The efficiency of the internal combustion engine can be expressed as ( )

[Analysis]To solve this problem, the key is to know the concept of heat engine efficiency and be able to look at the energy flow diagram of an internal combustion engine. The efficiency of a heat engine is the ratio of the energy used to do useful work to the energy released when the fuel is completely burned.

5. In order to save energy, it is necessary to improve the efficiency of the heat engine. Which of the following measures cannot improve the efficiency of the heat engine ()

A. Try to burn the fuel as fully as possible

B． Minimize friction between heat engine components

C. Minimize the heat taken away by exhaust gas

D. Maximize the working time of the heat engine

Keywords: Free download of PPT courseware for ninth-grade physics from the People's Education Press, PPT download on the efficiency of heat engines, PPT download on the utilization of internal energy, .PPT format;

For more information about the PPT courseware "Utilization of Internal Energy and the Efficiency of Heat Engines", please click on the Utilization of Internal Energy ppt Efficiency of Heat Engines ppt tag.

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Update Time: 2024-07-07

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