17-03-2014, 04:51 PM
E M Waves and Transmission Lines
Introduction
Steady currents produce a steady magnetic field. Steady magnetic fields are magnetic
fields which are constant with time. These fields are also called static magnetic fields or
magnetostatic fields.
Magnetic fields have several applications. Some of them are listed below.
These fields are described by the magnetic field intensity, H and the magnetic flux
density, B. Thease are related by B=μH. in fact, most of the relations in magnetostatic are
derived from the knowledge of relations in electrostatics.
Steady magnetic fields are governed by Bio-Savart law ad Amper’s circuit law.
APPLICATIONS OF MAGNETOSTATIC FIELDS
Magnetostatic fields are used in
• Magnetic separators
• Particle accelerators like cyclotrons
• Development of motors
• Compasses
• Microphones
• Telephone ringers
• Advertising displays
• Velocity selector
• Mass spectrometer
• Transformers
• Television focus controls
• High speed velocitu devices
• Magnetohydrodynamic generator
• Electromagnetic pump and so on.
2 Fundamentals of steady magnetic fields
Steady magnetic fields are also called static magnetic fields or magnetostatic fields.
These are produced by a magnet or by a current element. It is well known that loadstone
is a natural magnet. But it is a fairly weak magnet. Strong magnets are made of iron,
nickel, cobalt, or steel. These two opposite ends of a magnet are called its poles(Fig 1)
APPLICATIONS OF EM WAVES
They have a wide range of application in all types of communications like police
radio, television, satellite, ionospheric, topospheric, wireless, cellular, mobile
communications and so on and in all types of radars like Doppler radar, MTI radar, speed
trap radar, airport surveillance radar, weather forecasting radar, remote sensing radar,
ground mapping radar, IFF radar, astronomy radar, fire control radar and so on. EM
waves are also used in radiation therapy, microwave ovens and others.
Advantage in using EM waves for communication purposes is that the medium
between the transmitter and receiver requires no maintenance. This is because free space
is the best medium for EM wave propagation.