26.1 Magnetic Field Define magnetic field. Identify magnetic field sources.Sketch the magnetic field lines.
3Magnetic FieldA region around a magnet where a magnetic force can be experienced.A stationary electric charge is surrounded by an electric field only.Magnetic field has two poles:Poles (N-N or S-S) repel each otherPoles (N-S or S-N) attract each other
46.1.1 Magnetic Field Lines Used to represent a magnetic field Magnetic field lines leave the north pole and enters the south poles of the magnets
5• • • • • • • Magnetic field lines leave the page perpendicularly Magnetic field lines can be represented by crosses or by dotted circlesx x x x x x x x x x x x x x Magnetic field lines enter the pages perpendicularly• • • • • • • Magnetic field lines leave the page perpendicularly
6A uniform field is represented by parallel lines of force The number of lines passing perpendicularly through unit area at all cross sections in a magnetic field are same.
7A non uniform field is represented by non parallel lines of force The number of magnetic field lines varies at different unit cross-section area.The number of lines per unit cross sectional area is proportional to the magnitude of the magnetic fieldMagnetic field lines do not intersect one anotherWeaker field line in AStronger field line in B
86.1.2 Magnetic Field Lines Pattern The pattern of the magnetic field lines can be determined by using :Sprinkling iron filling on paperCompass needles
9The Various Pattern Of Magnetic Field Lines Around The Magnet Bar magnet
11Two bar magnet (unlike poles) – attract Two bar magnet (like poles) - repel
126.1.3 Earth’s Magnetic field A giant bar magnet with pole near each geographic pole of the earth.The magnetic poles are lifted away from the rotational axis by an angle of 11.5˚.The north pole of a compass needle points toward the north magnetic pole of the EarthThe north geographical pole of the Earth is actually near the south pole of the Earth’s magnetic fieldThe field lines are horizontally near the equator but enter or leave Earth vertically near the pole