Magnetic field in a surrounding space is produced by a
moving charge or a current. Magnetic field causes any other moving charge or
current that is present in the field to experience a force and it’s a vector
Permanent magnet is a magnetized
material that produces a constant magnetic field in a closed loop. The magnetic
field is always directed from North pole to South pole of the magnet. Magnets
are normally made from ferromagnetic materials such as iron (Fe), nickel (Ni),
and cobalt (Co). The magnetic strength of a magnet is measured by total magnetic
flux density produced (B). Different materials do have different flux density.
In a magnet, there is always two poles, North Pole and South Pole. Like poles always
repels each other while unlike poles always attract each other.
Solenoid is a long
helical coil of wire usually copper wire coiled into number of loops. When electric
current pass through the solenoid, magnetic field is produced creating an electromagnet.
Each ends of the electromagnet have a different pole depending on direction of
current flow. Polarity of the
electromagnet can be determined by using right hand grip rule. Magnetic field
strength of electromagnet is proportional to the magnitude of current passing
through the wire, the number of loops of wire, and cross-section of each
loop. Magnetic field strength (B) in a electromagnet can be described by:
is magnetic field strength, N is the number of
loops of wire,
is the permeability
of free space,
is the magnitude of current across the
solenoid, and L is the length of solenoid.
Iron core is usually inserted
into solenoids of the electromagnet causing the magnetic strength to increase
by tens to thousands of folds. The ferromagnetic property of the iron core
causes the internal magnetic domains of the iron to line up with the smaller
driving magnetic field produced by the current in the solenoid.