## Magnetic field

Magnetic field means that the state of the space where attraction or repulsive force are working.

For example,Iron sand is famous.

A magnet arranges iron sand to a circle-like pattern.

The magnetic field affects to this.

The magnetic field certainly exists around the place where through which electric current is flowing.

In short,there is magnetic field around TV and PC...

The unit is T which expresses a power of a magnetic field.

## The equation about magnetic field

There are some equations...but
we introduces two equations.

### Ampere's law

This equation means that relation between electric current and a magnetic field. is Ampere`s law.

I=current、r=distance、H=a power of magnetic field Andre = Marie Ampere is a French physicist and a mathematician.

Also,he found that Ampere`s right-handed screw rule.

• Ampere`s right-handed screw rule If the direction of electric current is The tip of a right-handed screw,

magnetic field would happen in the direction of a right-handed screw.

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### Biot-Savart law

This equation needs when we calculate the magnetic field which occurs by electric current.

Then,we explain easily or is Biot-Savart law.

|d|=Current element、r=distance、Km=Constant

This equation is found by two person.
• Jean-Baptiste Biot is a French physicist, an astronomer, and a mathematician.
• F?lix Savart is a French physicist,and a surgeon.

(Jean-Baptiste Biot)  【Reference】

http://www.tele.soumu.go.jp/kids/time2/time2.htm
http://ja.wikipedia.org/wiki/アンドレ＝マリ・アンペール
http://ja.wikipedia.org/wiki/ジャン＝バティスト・ビオ

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