Principle Of Generation Transmission And Reception Of Electromagnetic Waves

.The electromagnetic waves are generated when electrical or magnetic flux is changing through a
certain region of space

. An electric charge at rest give rise to a column field which does not ready 8 electromagnetic wave in space because no change of   Falak takes place in this type of field.

. A charge moving with constant velocity is equivalent to a Steady Current with generated a consist
magnetic field in the surrounding space, but such a field also does not read it out electromagnetic
waves because no change of magnetic flux are involved.

. We accelerate the electrical charge electromagnetic waves are generated because of the change
the of magnetic flux are involved .

. Rradio transmitting antenna is a good example for generating the electromagnetic waves by the acceleration of charges.

. The piece of wire along which charges are made to accelerate is know as transmitting antenna.
it is charged by an alternating source of potential of frequency f and time period t. as the charging
port candle alternates the charge on container also constantly the verses. this changing electrical flux
sets of electromagnetic wave which propagate out in space away from the antenna. the frequency
with which the field alternate is always equal to the frequency of the source generating them.

radio waves are produced. in free space these waves travel with the speed of light.

. When radio waves fall on a piece of wire, the electrons in the wire move under the action of the accelerating magnetic field. it produce an EMF or voltage across  the wire. this frequency of this EMF or voltage is the same as that of the wave intercepting the wire. the wire receiving the wave
is know as receiving antenna.

. The voltage of one particular frequency can be picked up by the connecting and inductance  l and
a variable capacitor c in parallel with tune and of the receiving antenna. the electrical field of the wave
is very weak at a distance of many kilometres from the transmitter, the voltage that appears Across
the antenna is very small.

. Each transmitter propagates radio waves of one particular frequency. so when a number of transmitting stations operators simultaneously,We have a number of radio waves of different frequencies in space. half the voltage that affairs across receiving antenna placed in space is usually due to the radio waves of large number of frequencies. the voltage of one particular frequency can be picked up by connecting and Indicator and a variable capacitor is parallel with one and receiving antenna.

. We adjust the value of the capacitor so that the natural frequency of LC circuit is the same as that
of the transmitting station that product of iresonance . the LC circuit gives a large response to dash
radio wave to which it is tuned.

. In our radio receiver that when we change station we usually adjust the value of the capacitance.