# Question about Electromagnetic Wave Induction into Receiving Antennas

• thentangler
The power source (in this case the antenna) provides the force to make them move back and forth. In summary, the conversation discusses the mechanism of how an antenna works and specifically focuses on how the receiving antenna converts oscillations of electrons to current. The conversation also touches on topics such as EM waves, photon energy, and the completion of the circuit in the receiving antenna. The general consensus is that the antenna acts as an AC generator, providing the force to make electrons move back and forth in the wire and completing the circuit. The conversation also clarifies that in an AC current, there is no depletion of electrons.

#### thentangler

Hey there everybody.

I have a question which till date no professor has been able to answer. At least as far as I know.
Its a basic antenna question.

We all know that any moving charged particle generates EM waves. That is how an antenna works, when the electrons on the antenna are excited at a particular freq, they generate EM waves of that freq. That travels to a receiving antenna and induces oscillations of the electrons in THAT antenna at the same freq. My question is:
How does the receiving antenna convert the oscillations of the electrons to current? There is no transfer of electrons from the transmitting antenna to the receiving one, only EM radiation. And the electrons from the antenna are not fed into the circuits which drive a radio or LEDs which light up when EM waves strike it, like the stickers you stick on your cell phones, and which light up when ever you make or receive a call.

This site might make it clear if I've confused you
http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=7566

But it talks only about the transmitting side. My question is on the receiving side.
I really appreciate it if anyone could hlpe me out.
Thanks a lot.

thentangler said:
My question is:
How does the receiving antenna convert the oscillations of the electrons to current?

What do you think a current is ?

Antenna gives off radio waves. Radio waves = EM wave = Photon = Energy (E = hf). The energy from the photon is given to a electron in the other antenna creating current.

In a conducting rod antenna, the E field of the EM wave creates an AC EMF in the rod.
In a loop antenna, the B field of the EM wave creates a changing flux through the loop,
giving an EMF by Faraday's law.

Thanks for the replies guys.
@ Clem,
How is the AC EMF fed to the circuitry of the reciever once it passes thru the antenna stage?
Is there a terminal EMF or something which is created at the feedline of the antenna? After that how does it get into the circuit?
I know very well that the current (i.e movement of electrons) which flows into the amplifier modules of your standard radio, does NOT come from the receiving antenna.

Thanks

The antenna just acts like an AC generator in the circuit.

thentangler said:
I know very well that the current (i.e movement of electrons) which flows into the amplifier modules of your standard radio, does NOT come from the receiving antenna.

Of course it does. This is an AC current at the RF carrier wave frequency, so the electrons in the antenna and coax cable and input to the receiver amp are all oscillating at the RF carrier wave frequency. The electrons in the metal antenna are experiencing the periodic force from the EM wave going by, and that force is what causes the motion of those electrons, which causes the propagation of the wave (AC motion of the electrons) in the coax cable connected between the antenna and the receive amp input.

Then how is the circuit completed?
Cos the circuit is grounded. And I am pretty much sure there is no depletion of electrons.
the electrons can't be replenished from the air, cos antenna works in space also!

thentangler said:
Then how is the circuit completed?
Cos the circuit is grounded. And I am pretty much sure there is no depletion of electrons.
the electrons can't be replenished from the air, cos antenna works in space also!
It's AC! There is no "depletion of electrons".

I know I am asking a really dumb question. But can you please explain how electrons move in an Alternating Current through a circuit?

They literally just move back and forth in the wire.

## 1. What is electromagnetic wave induction?

Electromagnetic wave induction is the process by which an electromagnetic wave, also known as a radio wave, creates an electric current in a receiving antenna. This process is the foundation of all radio communication and is based on the principles of electromagnetism.

## 2. How does electromagnetic wave induction work?

Electromagnetic wave induction works by using a transmitter to send out a radio wave, which is picked up by a receiving antenna. The radio wave creates an alternating electric current in the antenna, which is then amplified and decoded by a receiver to produce the desired audio or visual signal.

## 3. What factors affect the induction of electromagnetic waves into receiving antennas?

The induction of electromagnetic waves into receiving antennas can be affected by several factors, including the frequency of the wave, the size and shape of the antenna, the distance between the transmitter and receiver, and any obstacles or interference in the surrounding environment.

## 4. What is the role of the receiving antenna in electromagnetic wave induction?

The receiving antenna plays a crucial role in electromagnetic wave induction as it is responsible for capturing the radio wave and converting it into an electric current. The design and positioning of the antenna can greatly impact the effectiveness of the induction process.

## 5. What are some practical applications of electromagnetic wave induction?

Electromagnetic wave induction has a wide range of practical applications, including radio and television broadcasting, wireless communication, radar systems, and wireless power transfer. It is also used in scientific research and medical imaging technologies such as MRI machines.