earth's magnetic field問題!!

2008-04-10 9:23 pm

Which of the following statements correctly explain(s) why the earth's
magnetic field has no effect on the compass kept inside a closed soft iron box?

(1)Soft iron is a metal
(2)Soft iron can be magnetised
(3)The space inside the soft iron box is shielded from the surrounding
magnetic field

隨便問埋,
be magnetised即係咩意思???

點解指南針會受earth's magnetic field,指出方向
但iron唔會俾吸引住???

thx~~~~~~

回答 (1)

天同

2008-04-15 4:27 am

✔ 最佳答案

The answer is Statement (3), soft iron could shield off external magnetic fields.

[be magnetized] means 被磁化.

A compass needle is itself a small bar magnet. It has [North] and [South] poles. Since [North] pole will move along the direction of magnetic field lines and [South] pole moves against the field line direction, the compass needle will eventually settle in a position such that the [North] pole is towards the north and [South] pole towards the south.

Iron is a ferromagnetic material. It is NOT a magnet unless it is magnetized by some means.

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