MAGNETIC f IELD 6 1 Magnetic Field Define

MAGNETIC f. IELD

6. 1 Magnetic Field �Define magnetic field. �Identify magnetic field sources. �Sketch the magnetic field lines.

Magnetic Field • A 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 other • Poles (N-S or S-N) attract each other

6. 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

Magnetic field lines can be represented by crosses or by dotted circles xxxxxxx x Magnetic field lines enter the pages perpendicularly • • • • • Magnetic field lines leave the page perpendicularly

� A 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.

� A 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 field Weaker field line in A Stronger field line in B � Magnetic field lines do not intersect one another

6. 1. 2 Magnetic Field Lines Pattern � The pattern of the magnetic field lines can be determined by using : 1. Sprinkling iron filling on paper 2. Compass needles

The Various Pattern Of Magnetic Field Lines Around The Magnet �Bar magnet

�Horseshoe or U magnet

�Two bar magnet (unlike poles) – attract �Two bar magnet (like poles) - repel

6. 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 Earth � The north geographical pole of the Earth is actually near the south pole of the Earth’s magnetic field � The field lines are horizontally near the equator but enter or leave Earth vertically near the pole