"Magic Compass" Preparation PPT courseware before the inspection

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"Magic Compass" Preparation PPT courseware before the inspection

A compass is an instrument that uses magnets to indicate direction

The principle of compass

The compass is a guiding instrument invented in ancient my country that uses the polarity of magnets. Therefore, we must start with the magnet.

As early as the Han Dynasty more than 2,000 years ago, the Chinese discovered that a stone on the mountain had the magical property of attracting iron, and discovered that a long stone could guide north and south. They called this stone a magnet.

Skilled craftsmen in ancient times polished and carved the magnet into a spoon shape, placed it on a smooth mirror-like chassis, and then cast directional carvings on it. This magnetic spoon can rotate freely on the chassis. When it stops rotating, the handle of the spoon points in the direction of true south, and the mouth of the spoon points in the direction of true north. This is the world's earliest direction-indicating instrument invented by our ancestors, called Sinan. It is the world's earliest "compass". Among them, "Si" means "finger".

How to use Sinan

When using it, first lay the land flat, then place Simon in the middle of the land, turn the spoon handle with your hand to make it rotate, and when Simon stops, the direction the spoon handle points to is south.

This spoon-shaped sinen was still in use until the eighth century.

guide fish

By the Song Dynasty, people had mastered the technology of making artificial magnets and made guide fish.

The guide fish is made by cutting a thin steel sheet into a fish shape, two inches long and five minutes wide. The belly of the fish is concave so that the fish can float on the water like a boat. You can tell the direction by placing the guide fish on the water.

compass

Later, people learned to make magnets artificially and made magnetic needles. They placed the magnetic needle in a plate filled with water and marked the direction on the edge. The magnetic needle floats on the water and can rotate freely. When it is stationary, its two ends point in the north and south directions respectively. This kind of guide instrument is a step further than Sinan. It is easier to make and more sensitive. People call this guiding instrument a water compass, also called a compass.

1. What parts does a compass consist of?

2. Which end of the magnetic needle points to north and which end to guide?

3. How is the direction indicated on the steering wheel?

Observation: How many basic structures does a compass have?

Box: protection

Magnetic needle: determine N and S poles.

Orientation disk: guide to determine other specific directions.

Bracket: supports the magnetic needle to keep it horizontal.

Why does a compass indicate north and south directions?

The earth is a big magnet.

The geomagnetic pole near the Earth's North Pole is the South Pole,

The geomagnetic pole near the Earth's South Pole is the North Pole.

The compass is affected by the magnetic force in the earth's magnetic field, so one end points to the north and the other to the north.

How to use a compass to determine direction

1. Lay the compass box flat and let the magnetic needle rotate freely.

2. After the magnetic needle stops swinging, turn the compass box so that the south (S) and north (N) directions marked on the steering wheel are consistent with the north-south direction of the magnetic needle.

3. Determine each direction according to the azimuth dial.

Look at what direction our school doors face and what direction our classroom windows face.

Class exercises:

1. A compass is an instrument that uses ( ) to indicate direction. Generally, compasses are composed of ( ) and ( ).

2. What is known as the world’s earliest “compass” is ( ), which is one of the four great inventions in ancient my country.

Questions and Answers:

How to determine direction with a compass?

1. Lay the compass box flat and let the magnetic needle rotate freely.

2. After the magnetic needle stops swinging, turn the compass box so that the south (S) and north (N) directions marked on the steering wheel are consistent with the north-south direction of the magnetic needle.

3. Determine each direction according to the azimuth dial.

How to quickly determine the north and south poles of a bar magnet using a compass.

Method 1: Use a magnet to attract the compass. The end that attracts the north pole of the compass is the south pole of the magnet. The end that attracts the south pole of the compass is the north pole of the magnet.

Method 2: First use a compass to determine the north-south direction, then hang up the magnet and observe the direction of the magnet when it stops.

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Update Time: 2024-11-22

This template belongs to science courseware People's Education Press Fourth Grade Science Volume 1 industry PPT template

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