Power Output of Radiation from a Solenoid with Linearly Decreasing Current

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SUMMARY

The discussion focuses on the power output of electromagnetic radiation from a solenoid with 610 cycles, a radius of 0.136m, and a length of 0.87m, where the current decreases linearly from 0.31 A to zero. The current is modeled by the equation I(t) = I0 - bt, with b set at 0.21 A/s. Participants express skepticism regarding the solenoid's ability to radiate significant energy, particularly given its length and the low frequency of approximately one Hertz, suggesting that the energy is primarily stored within the electric and magnetic fields rather than emitted as radiation.

PREREQUISITES
  • Understanding of electromagnetic theory
  • Familiarity with solenoid properties and behavior
  • Knowledge of current decay equations
  • Basic principles of electromagnetic radiation
NEXT STEPS
  • Investigate the relationship between solenoid dimensions and radiation efficiency
  • Learn about the Poynting vector and its role in electromagnetic radiation
  • Explore the implications of current decay on electromagnetic field behavior
  • Study the conditions under which electromagnetic radiation is emitted from inductors
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Students in physics or electrical engineering, researchers studying electromagnetic radiation, and professionals involved in designing solenoids or related electromagnetic devices.

Jaakko
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Homework Statement


A solenoid contains 610 cycles, with a radius of 0.136m and a length of 0.87m. The current of the solenoid decreases linearly from the maximum value I0 to zero through the equation I(t)=I0−bt, where I0=0.31 A and b=0.21 A/s.

What is the power output of the electromagnetic radiation at t= 0.738095238095?

Homework Equations


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The Attempt at a Solution


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I am unclear why a solenoid about one metre long will radiate any significant energy when the supposed frequency is in the order of one Hertz, a wavelength of 3x10^8 metres? The presence of electric and magnetic fields does not mean there is radiation. The fields of the solenoid contain energy that is almost entirely stored and not radiated.
 

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