Slide 1

MAGNETIC fIELD6.1 Magnetic FieldDefine magnetic field.

Identify magnetic field sources.

Sketch the magnetic field lines.

Magnetic 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

6.1.1 Magnetic Field LinesUsed to represent a magnetic fieldMagnetic 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

x x x x x x x x x x x x x xMagnetic field lines enter the pages perpendicularly

Magnetic field lines leave the page perpendicularlyA uniform field is represented by parallel lines of forceThe 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 forceThe 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

Magnetic field lines do not intersect one another

Weaker field line in AStronger field line in B6.1.2 Magnetic Field Lines PatternThe pattern of the magnetic field lines can be determined by using :Sprinkling iron filling on paper

Compass needles

The Various Pattern Of Magnetic Field Lines Around The MagnetBar magnet

Horseshoe or U magnet

Two bar magnet (unlike poles) attract

Two bar magnet (like poles) - repel

6.1.3 Earths Magnetic fieldA 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 Earths magnetic fieldThe field lines are horizontally near the equator but enter or leave Earth vertically near the pole