Hertz Experiment to produce Electromagnetic waves


Hertz Experiment

Hertz Experiment   is an important topic to know , when dealing with the concept of Electromagnetic waves . This experiment played a major role in their production. Electromagnetism is incomplete without Hertz Experiment.

Today I write  article  "Hertz Experiment   to produce electromagnetic waves". The article provide you an exact and brief information. It would cover topics like Hertz Experiment   and follow up of the work. 

"Hertz Experiment to produce Electromagnetic waves ":

German scientist H.R.Hertz in 1887 ,first of all gave a practical demonstration of the production of Electromagnetic waves using an oscillatory circuit. Hertz Experiment   was based on the fact that a vibrating electric charge radiates Electromagnetic waves. He produced Electromagnetic waves in the laboratory . Hertz used the  arrangement shown in the figure for the production of Electromagnetic waves.

Hertz Experiment  , experimental arrangement
Hertz Experiment  

The arrangement consists of a two large metallic plates. The metallic plates are denoted as P₁ and P₂  connected to an Induction coil .  Two metallic spheres are also used in the arrangement. They are denoted as S₁ and S₂. These metallic spheres are connected to the metallic plates.

A small air gap separates these two metallic spheres. The metallic spheres behaves like a capacitor of capacitance C. This circuit is know as transmitter. Hertz used a single loop of wire in the arrangement. Hertz connected the single loop of wire to spheres S₁ ̍ and S₂ ̍, away from the transmitter. This circuit is know as receiver.

In fact,  we can say that a transmitter is an L-C circuit. The L-C circuit gives rise to Electromagnetic waves due to transfer of energy. The energy gets transferred from the electric field of the capacitor to the magnetic field of the inductor (i.e.,  Induction coil).


Let at t=0, capacitor is fully charged so that it has maximum charge and zero current. But when the capacitor begins to discharge, electric field is converted into the magnetic field of the inductor. When capacitor is fully discharged,  it has zero charge and current in the circuit becomes maximum.

The whole process is repeated in the reverse direction. Therefore , the energy continues to transfer between the capacitor and the Inductor. Corresponding to the oscillations in the charge and the current in the L-C circuit.

Remember, when the spheres S₁ and S₂ of the transmitter are charged oppositely, the spark between S₁ and S₂ gives rise to oscillations of charge which in turn send out Electromagnetic waves. The frequency of oscillation is given as:

                                                       υ = 1/2π√LC

The succession of sparks sends out a train of such waves which are received by receiver. 

Hertz Experiment  successfully produced the Electromagnetic waves of about 6 metre wavelength. 

" Follow up of Hertz work ":

The Electromagnetic waves produced in Hertz Experiment   were of large wavelength. Therefore, of a very small frequency . The Electromagnetic waves so produced in Hertz Experiment could not be detected over a large distance. 

Just seven years after Hertz Experiment ,  an Indian scientist named J. C. Bose succeeded in producing and observing Electromagnetic waves of very short wavelength. The wavelength of these waves ranges from 25 mm to 5 mm. But his experiment remained confined to the laboratory.

In 1895, another well known scientist named "Marconi" made an important discovery which helped in producing Electromagnetic waves of commercial value. He got a success in transmitting these Electromagnetic waves up-to a few kilometer. This experiment resulted the use of Electromagnetic waves in the field of communication.

A simple oscillator comprising L-C circuit and energy source can produce waves of different frequencies . These waves are produced by changing the values of capacitance and inductance. To produce oscillations of undamped nature. some energy of the same frequency is required to be pumped in or fed back to the oscillator circuit .

These undamped oscillations are then taken to a transmission line  connected to an aerial or antenna. Most efficient antennas are those which have a size comparable to the wavelength of Electromagnetic wave. The waves they emit or receive. The A.C power source has to deliver the required power at the rate required for radiation of Electromagnetic wave energy.

A simple arrangement for the production and transmission of Electromagnetic waves is shown in the figure.

Hertz Experiment  , follow up of Hertz work
Hertz Experiment  


The article as you know written above has discussed about the production of Electromagnetic waves with the help of Hertz Experiment. The article provides you a brief and complete information about Hertz Experiment.

However, the article has also discussed about " Follow up of Hertz Experiment".
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