"Conversion and Conservation of Energy" Utilization of Internal Energy PPT Courseware 4

"Conversion and Conservation of Energy" Utilization of Internal Energy PPT Courseware 4

teaching objectives

1. Know the law of conservation of energy

2. Can give examples of energy conservation in daily life

3. Be able to analyze physical phenomena from the perspective of energy conservation

chemical energy

1. The combustion of fuel is a chemical change. The light and heat generated during combustion come from the chemical energy stored in the fuel.

2. Food also has chemical energy. The energy consumed in people’s lives and work comes from the chemical energy stored in food.

1. Various forms of energy:

Mechanical energy, electrical energy, internal energy, light energy, chemical energy, nuclear energy

Question: Can various forms of energy be converted into each other?

in conclusion:

Under certain conditions, various forms of energy can be converted into each other.

Energy can be transferred from one object to another:

①Instances of mechanical energy transfer from one object to another

The collision of two small balls gives the stationary ball an initial velocity.

②Instances of transferring electrical energy from one object to another

The generator generates electricity to make the light shine

③Instances of transfer of internal energy from one object to another

Keep warm by the stove

summary:

Under certain conditions, various forms of energy can be converted and transferred to each other.

2. Law of conservation of energy:

Energy will neither be destroyed nor created out of thin air. It will only be converted from one form to other forms, or transferred from one object to another. In the process of transformation and transfer, the total amount of energy remains unchanged. Change.

practise

1. Point out the transformation or transfer of energy in the following phenomena:

(1) Photosynthesis of plants;

(2) Thunder and lightning occur on rainy days;

(3) When people run, their bodies heat up and sweat;

(4) The hand-cranked generator generates electricity to make the light bulb shine.

Analytical thinking:

1. A cup of hot water placed on the table is cooled. Is there any possible transformation in this process? Has the heat energy of the hot water disappeared?

2. When the electric fan is working, is the electrical energy consumed equal to the mechanical energy obtained by the motor? So where does the rest of the electricity go?

3. There is a saying in our country: "You want the horse to run, but you also want the horse not to eat grass." Do you think this is possible? Why?

3. Unrealizable “perpetual motion machine”

1. "Perpetual motion machine": A machine that does not consume any energy or fuel, but continuously performs work on the outside.

2. According to the law of conservation of energy: it cannot be realized.

3. The task of engineering technology is to find ways to rationally utilize energy and reduce unnecessary energy loss during machine operation, rather than to develop a "perpetual motion machine" that can never be realized.

practice

1. A rifle is aimed at a high altitude, the trigger is pulled and a bullet is fired. The bullet misses the target and finally falls and sinks into the ground. Please tell me what energy transformations occurred during the above process.

2. Please specify the meaning of the following efficiency from the perspective of energy conversion.

● The efficiency of a certain solar cell is 16% when working

● The working efficiency of a certain electric motor is 83%

● The charging efficiency of a certain lithium battery is 99%

● The working efficiency of a certain diesel engine is 35%

● The working efficiency of a certain electric water heater is 87%

3. Conservation of energy is one of the basic laws of nature. In the following energy conversion processes, the transfer of internal energy is ()

A. lighting with electric light

B． photosynthesis

C. Keep warm with a hot water bottle

D. combustion of natural gas

Exercise 1

1. Ice cubes slide along the ground and tend to melt gradually. In this process, _____ energy is converted into _____ energy.

2. The energy sources of the sun and hydrogen bombs are _______ nuclear power plants and atomic bombs.

3. During the day, the temperature of the water in the solar water heater rises, and the internal energy of the water _______ (fill in "decrease," "unchange," or "increase"). This changes its internal energy through _______.

Exercise 2

1. In the process of mutual conversion of various forms of energy, which of the following statements is correct ( )

A. Mechanical energy must be conserved

B. All forms of energy are conserved

C. The total amount of various forms of energy must be conserved

D. Only mechanical energy is converted into internal energy

2. The process of photosynthesis in plants is ( )

A. Light energy is converted into chemical energy B. Internal energy is converted into chemical energy

C. Chemical energy is converted into light energy. D. Light energy is converted into internal energy.

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