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  Physics (NTSE/Olympiad)  

2. Magnetic Effect of Current

Types of Magnets, Permanent (Natural & Artificial magnets)

Types of Magnets
(A) Permanent (Natural & Artificial magnets)
(B) Temporary (Electromagnets)
(A) Permanent (Natural & Artificial magnets)
Natural Magnets
Definition : Pieces of naturally occurring iron ore lode–stone or magnetic or black iron oxide (Fe2O3) are called natural magnets.
Properties : These have following two properties.
(i) Attractive property: They attract small iron pieces towards them.
(ii) Directive property: When suspended freely, their ends would point in geographical north–south direction. For this reason, the suspended piece is called lode stone or leading stone.
Disadvantage : These have following two demerits :
(i) They have irregular shape.
(ii) They are weak.
Artificial Magnets
Description : These magnets are made of hard steel or special alloys. The substances of these magnets have many small ‘atomic’ magnets. Ordinarily they are all oriented in random directions (Fig.). Then the substance is unmagnetised

(a) Unmagnetised

(b) Magnetised
When such a piece is put in North–South direction and hammered, the atomic magnets align themselves in the direction of the earth’s field fig. They retain this alignment and the piece becomes a magnet with North (N) and (S) pole near ends. This magnet with two poles, is called a magnetic dipole .
Advantage : These have following two merits
(a) They may be given desired regular shape.
(b) They are strong.

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