"Conversion and Conservation of Energy" Energy, Materials and Society PPT Courseware 3

"Conversion and Conservation of Energy" Energy, Materials and Society PPT Courseware 3

Situation introduction

Can you tell what form of energy the following objects have?

1. Conversion of energy

Think about it, do it

1. Rub your hands quickly back and forth.

2. Rub the holder of the pen on your hair or sweater and then move it closer to the small piece of paper.

Observe the phenomena that occurred in the experiment and discuss what energy transformations occurred?

Can you give some other examples where you think energy transformations occurred? Please name the energy transformation you think occurred.

in conclusion:

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

1. Energy transfer from one object to another

2. Conversion of energy from one form to another

2. Law of conservation of energy

Want to discuss

1. What does it mean that the height of the ball gradually decreases?

It shows that the mechanical energy of the ball gradually decreases.

2. Where does the reduced mechanical energy go?

The ball rubs against the air and the ground, and part of the mechanical energy is converted into internal energy.

Energy conservation law

A large number of facts show that 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 other objects. In the process of transformation and transfer, the total amount of energy The quantity remains unchanged.

The law of conservation of energy is one of the most universal and important basic laws of nature.

discuss

1. How is energy transformed during the skating and slide process? Does it obey the law of conservation of energy?

2. Someone once imagined making a machine that can continuously do work without power. People call this kind of machine a perpetual motion machine.

3. Directionality of energy transfer and energy conversion

Since energy is conserved, the energy on the earth will not decrease. Why do we need to save energy?

We refine gasoline from petroleum, and the internal combustion engine converts the chemical energy stored in the energy into the mechanical energy and internal energy of the car.

This mechanical energy and internal energy cannot be converted back into energy that can be utilized.

Thermal power plants convert the chemical energy stored in coal into electrical energy for production and daily use.

After using electrical appliances to convert electrical energy into various forms of internal energy, light energy, and mechanical energy, this energy cannot be converted back into energy.

practice

1. Among the following examples, the conversion of mechanical energy into internal energy is ( )

A. The iron rod is very hot on the fire

B. The car brakes suddenly and the tires heat up

C. Burning wood for heating

D. Energize the electric furnace and the electric furnace generates heat.

2. In the process of various forms of energy conversion, 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

3. 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.

4. True or False Questions

1. During the combustion process of coal, the chemical energy of coal is converted into internal energy, but the total amount of energy remains unchanged. ( )

2. When swinging, stop exerting force. The swing will swing lower and lower, and the total amount of energy will become less and less. ( )

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