Class 9 ICSE PHYSICS ||Magnetism ||ONE SHOT VIDEO ||Chapter-10 ||Full Chapter скачать в хорошем качестве

Class 9 ICSE PHYSICS ||Magnetism ||ONE SHOT VIDEO ||Chapter-10 ||Full Chapter

INSTAGRAM: https://www.instagram.com/physicsplaz... Lodestone is the first known pieces of magnets, an ore of iron oxide (Fe3O4) found in large quantities in Magnesia, in Asia Minor. The pieces of lodestone found in nature were called natural magnets. The limitations of a natural magnet are — They are found in quite irregular and odd shapes. They are not magnetically strong enough for use. *ARTIFICIALMAGNETS:Artificial magnets are prepared from iron in different convenient shapes and sizes. Examples of artificial magnets are bar magnet, horse shoe magnet, magnetic needle and magnetic compass. We need artificial magnets because — Natural magnets are of irregular and odd shapes. Natural magnets are not magnetically strong enough for use. INDUCED MAGNETISM: The temporary magnetism acquired by a magnetic material when it is placed near (or in contact with) a magnet, is called induced magnetism. EXAMPLE:When two pins are hung by their heads from the same pole of a magnet, their pointed ends move apart because the iron nails by magnetic induction gets magnetized and develop same poles. As we know that like poles repel each other hence, the two pointed ends of the nails repel each other. MAGNETIC FIELD LINES-PROPERTIES: A magnetic field line is a continuous curve in magnetic field such that tangent at any point of the curve gives the direction of the magnetic field at that point. They are closed and continuous curves. Outside the magnet, they are directed from the north pole towards the south pole of the magnet. The tangent at any point on a field line gives the direction of magnetic field at that point. They are crowded near the poles of the magnet where the magnetic field is strong and far away near the middle of the magnet and far from the magnet where the magnetic field is weak. The iron fillings which are sprinkled on a sheet of cardboard placed over a bar magnet, take up a definite pattern when cardboard is slightly tapped because each piece of iron fillings gets magnetized by magnetic induction and experiences a force due to the magnet. Therefore, they arrange themselves along curved lines and these curved lines are called magnetic field lines. The evidences of the existence of earth's magnetic field are — (1)A freely suspended magnetic needle always rests in geographic north-south direction. (2)An iron rod buried inside the earth along north-south direction becomes a magnet. NEUTRAL POINTS: Neutral points are the points at which two magnetic fields are equal in magnitude, but opposite in direction. The net magnetic field at a neutral point is zero. A compass needle if placed at the neutral point, will rest in any direction. Hence, we can find the position of neutral points with the help of compass needle. (i) When a magnet is placed with it's axis in the magnetic meridian and with it's north pole pointing towards the geographic north then the neutral point will be in east-west direction. (ii) When a magnet is placed with it's axis in the magnetic meridian and with it's north pole pointing towards the geographic south then the neutral point will be in north-south direction. ELECTROMAGNET: An electromagnet is a temporary strong magnet made from a piece of soft iron when current flows in the coil wound around it. It is an artificial magnet The strength of a magnet can be increased by — Increasing the number of turns of windings in the solenoid. Increasing the current through the solenoid. Advantages of an electromagnet over a permanent magnet are — An electromagnet can produce a strong magnetic field. The strength of the magnetic field of an electromagnet can easily be changed by changing the current (or the number of turns) in it's solenoid. Soft iron is used for making the armature of an electric bell because it acquires magnetic properties only when an electric current flows through the solenoid and loses the magnetic properties as soon as the current is switched off. The factors on which the strength of the magnetic field of an electromagnet depends are — The number of turns of wire wound around the coil — By increasing the number of turns of wire wound around the coil, the magnetic field of an electromagnet can be increased. The amount of current flowing through the wire — By increasing the current through the wire, the magnetic field of an electromagnet can be increased. Thanks to ‪@PhysicsWallah‬ ‪@physicsgalaxyworld‬ ‪@sachinsirphysics‬ ‪@PradeepKshetrapal‬ ‪@ProfKNageshwar‬ ‪@manojmalikphysics8393‬