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Learn about natural and artificial magnets, types of magnetism, methods of magnetization, and practical applications of electromagnetism. Discover how to maintain and protect magnets for long-lasting use.
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MANORMA GROUP OF EDUCATION • DIRECTED BY RAKESH SIR • CREATED BY • PRABHANSHU SHEKHAR
MAGNETISM चुम्बक (मैग्नेट्) वह पदार्थ या वस्तु है जो चुम्बकीय क्षेत्र उत्पन्न करता है। चुम्बकीय क्षेत्र अदृश्य होता है और चुम्बक का प्रमुख गुण - आस-पास की चुम्बकीय पदार्थों को अपनी ओर खींचने एवं दूसरे चुम्बकों को आकर्षित या प्रतिकर्षित करने का गुण, इसी के कारण होता है।
NATURAL MAGNET A lodestone is a naturally magnetized piece of the mineral magnetite.Theyare naturally occurring magnets, which can attract iron. The property of magnetism was first discovered in antiquity through lodestones.Piecesof lodestone, suspended so they could turn, were the first magnetic compasses, and their importance to early navigation is indicated by the name lodestone, which in Middle English means 'course stone' or 'leading stone', from the now-obsolete meaning of lode as ‘journey, way’.
ARTIFICIAL MAGNET • THOSE MAGNET WHICH ARE PRODUCED BY US FROM MAGNETIC MATERIALS ARE KNOW AS ARTIFICIAL MAGNET. E.G., BAR MAGNET , HORSE SHOE MAGNET ETC
चुम्बक के प्रकार • स्थायी चुम्बक • इनके द्वारा उत्पन्न चुम्बकीय क्षेत्र बिना किसी वाह्य विद्युत धारा के ही प्राप्त होता है। और सामान्य परिस्थितियों में बिना किसी कमी के बना रहता है। (इन्हें विचुम्बकित (डी-मैग्नेटाइज) करने के लिये विशेष व्यवस्था करनी पड़ती है।) ये तथाकथित कठोर (हार्ड) चुम्बकीय पदार्थ से बनाये जाते हैं। • अस्थायी चुम्बक
ये चुम्बक तभी चुम्बकीय क्षेत्र उत्पन्न करते हैं जब इनके प्रयुक्त तारों से होकर विद्युत धारा प्रवाहित की जाती है। धारा के समाप्त करते ही इनका चुम्बकीय क्षेत्र लगभग शून्य हो जाता है। इसी लिये इन्हें विद्युतचुम्बक (एलेक्ट्रोमैग्नेट्) भी कहते हैं। इनमें किसी तथाकथित मृदु या नरम (सॉफ्ट) चुम्बकीय पदार्थ का उपयोग किया जाता है जिसके चारो ओर तार की कुण्डली लपेटकर उसमें धारा प्रवाहित करने से चुम्बकीय क्षेत्र उत्पन्न होता है।
METHODS OF MAGNETIZATION • THERE ARE TWO METHODS FOR ARTIFICIAL MAGNET PREPRATION
MECHANICAL METHOD SINGLE TOUCH METHOD
DIVIDED TOUCH METHOD METHOD
Uses of electromagnetismElectric bellRelay to allow one circuit to operate anotherElectric motorsRecording heads in tape recorders, floppy discs and hard discsElectric analogue metersIn scrap yards for lifting metalsDeflector coils in televisionFor removing metal (ferrous) splinters from your eyesLoudspeakers and telephone earpieceNuclear acceleratorsLocking devices for safes
MAINTENANCE OF MAGNETS • When not using your magnetic sign keep it in a clean, dry place. • Stack flat magnetic signs on a level surface. • Avoid placing objects on top that could damage the face. • Do not stack signs with the magnetic side facing each other.
Protecting the magnet • Magnets can have either a coating or casing to protect them from any bumps or corrosion. One form of coating for a magnet - rubber, can be replaced when it becomes torn or cracked, for example, after being left exposed to the elements whilst being used as a car magnet.
CLASSIFICATION OF MAGNETIC MATERIALS • FERRO MAGNETIC MATERIALS • Ferromagnetic materials, such as iron, contain unpaired electrons, each with a small magnetic field of its own, that align readily with each other in response to an external magnetic field. This alignment tends to persists even after the magnetic field is removed, a phenomenon called hysteresis.
PARA MAGNETIC MATERIALS • Paramagnetism is a form of magnetism whereby certain materials are attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field.
DIA-MAGNETIC MATERIALS • Diamagnetic materials are repelled by a magnetic field; an applied magnetic field creates an induced magnetic field in them in the opposite direction, causing a repulsive force. In contrast, paramagnetic and ferromagnetic materials are attracted by a magnetic field. Diamagnetism is a quantum mechanical effect that occurs in all materials; when it is the only contribution to the magnetism the material is called diamagnetic. In paramagnetic and ferromagnetic substances the weak diamagnetic force is overcome by the attractive force of magnetic dipoles in the material. The magnetic permeability of diamagnetic materials is less than μ0, the permeability of vacuum. In most materials diamagnetism is a weak effect which can only be detected by sensitive laboratory instruments, but a superconductor acts as a strong diamagnet because it repels a magnetic field entirely from its interior. • Diamagnetism was first discovered when SebaldJustinusBrugmans observed in 1778 that bismuth and antimony were repelled by magnetic fields. In 1845, Michael Faraday demonstrated that it was a property of matter and concluded that every material responded (in either a diamagnetic or paramagnetic way) to an applied magnetic field. He adopted the term diamagnetism after it was suggested to him by William Whewell.[1]
MAGNETIC-FIELD OF A CURRENT CARRYING STRAIGHT CONDUCTORRIGHT HAND RULE