How is converted the energy of a E.M. wave in a conductor

In summary, when an electromagnetic wave passes through a conductor, the energy from the wave is converted to kinematic energy as the electrons in the conductor move. This can manifest as a current being generated in the wire. The conservation of energy in this process is not easily proven and may involve factors such as distributed L and C in the wire, resistance and reactance, and the creation of a magnetic field which stores energy and gives inertia to the electrons. The physical characteristics of the circuit can also affect the intercepted energy and result in effects such as a shadow or a reflection.
  • #1
happyparticle
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Homework Statement
How is converted the energy of a E.M. wave in a conductor
Relevant Equations
##u_i = u_e + u_m##
I'm thinking about how the energy is conserved when a E.M. wave pass through a conductor.
If a E.M. pass through a conductor, the electrons must move "oscillated", thus the energy from the E.M. wave is converted to kinematic energy.
Another way I see that is the E.M wave must generate a current.
I don't know if my intuition is correct, but either way, I can't prove the conservation of energy. The initial energy ##u_i = u_e + u_m \neq u_f + \frac{1}{2}mv^2##
I must forget something or it's not as simple as that.
 
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  • #2
The electric field of the wave creates a voltage along the wire. This then creates a current in the wire dictated by the resistances and reactances which are present. (Notice that a piece of wire has its own distributed L and C even without adding anything to make a circuit). When the current flows, it means that electrons have been accelerated, and when they do this they radiate. For a wire having no resistance, any energy which is intercepted will be re-radiated due to electron acceleration. For a wire in a circuit with resistance, some of the energy intercepted will be re-radiated, the remainder warming the resistor.
The electrons have very small mass, so KE is negligible, but when they move they create a magnetic field, and this stores energy as if it were a mass. This gives inertia, as if we had mass.
The inertia means that the acceleration of the electrons in response to an incoming wave may be delayed, in a similar way to current in an inductor. Phase shift also arises due to capacitance in the circuit. The re-radiated wave will combine with the incoming wave causing it to be weaker due to the intercepted energy. However, if the re-radiated energy is shifted in phase, the passing EM wave can exhibit effects such as a shadow, or a bright reflection.
Notice that the physical length, shape and components of the circuit will, in a complex way, influence the power which is intercepted.
 

FAQ: How is converted the energy of a E.M. wave in a conductor

1. How does an electromagnetic (E.M.) wave transfer energy to a conductor?

An E.M. wave consists of oscillating electric and magnetic fields. When it encounters a conductor, the changing electric field induces a current in the conductor. This current then experiences resistance, causing some of the energy from the E.M. wave to be converted into heat and dissipated.

2. What factors affect the efficiency of energy conversion in a conductor?

The efficiency of energy conversion in a conductor depends on several factors, including the material and properties of the conductor (such as its conductivity and resistance), the frequency and intensity of the E.M. wave, and the angle of incidence of the wave on the conductor.

3. Can all types of E.M. waves be converted into energy in a conductor?

No, only certain types of E.M. waves can be converted into energy in a conductor. This includes radio waves, microwaves, and infrared waves, which have lower frequencies and longer wavelengths. Higher frequency E.M. waves, such as visible light and X-rays, do not typically transfer energy to conductors.

4. What happens to the energy of an E.M. wave after it is converted in a conductor?

The energy of an E.M. wave that is converted in a conductor is primarily dissipated as heat. Some of the energy may also be reflected or transmitted through the conductor, depending on its properties and the properties of the E.M. wave.

5. How is the converted energy from an E.M. wave used in practical applications?

The converted energy from an E.M. wave in a conductor can be used in a variety of practical applications, such as in wireless charging, communication technologies, and heating systems. It can also be harnessed to generate electricity in devices like solar cells and antennas.

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