Electrical energy stored in solenoid

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SUMMARY

The discussion focuses on the energy stored in a solenoid's magnetic field when a current increases linearly over time. It establishes that the energy in the electric field is zero, as per Poynting's theorem, which states that the energy change in an electromagnetic system is the energy input minus the energy flowing out. The conversation emphasizes that in a quasi-static scenario, the energy remains in the magnetic field, and the relationship between electric and magnetic fields is fundamentally intertwined, challenging traditional views of their separation. The discussion also hints at the evolving understanding of these concepts through vector and scalar potentials.

PREREQUISITES
  • Understanding of Poynting's theorem in electromagnetism
  • Familiarity with solenoid operation and magnetic fields
  • Knowledge of electric and magnetic field interactions
  • Basic principles of vector and scalar potentials in physics
NEXT STEPS
  • Study Poynting's theorem in detail to grasp energy flow in electromagnetic systems
  • Explore the mathematical models of electric and magnetic fields
  • Learn about vector and scalar potentials and their implications in electromagnetism
  • Investigate the relationship between electric fields and induced magnetic fields in dynamic systems
USEFUL FOR

Physicists, electrical engineers, and students studying electromagnetism who seek to deepen their understanding of energy storage in electromagnetic fields and the interplay between electric and magnetic phenomena.

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I have a solenoid which has a current passing through it which increases linearly with time. I have proved that the energy stored in the magnetic field is equal to the energy being pumped in according to the surface integral of the poynting vector. This implies the energy stored in the electric field is zero (according to poynting's theorem which states the energy change for an EM system is the energy pumped into the E and B fields minus the energy flowing out of the surface in the poynting vector).
Why is the energy stored in the electric field zero? My attempt was that in a static situation (constant current I), the energy is entirely in the magnetic field since there is no electric field, so if we take this linear increase in a quasi-static manner, then the energy stored in each quasi-static situation should be equivalent to the same static situation, so it wouldn't make sense if energy was stored in the E-field in one situation but not in the other.
 
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Although there is no magnetic field in the final state, there is a nonzero induce magnetic field when you increase the electric field from zero to the desired value. I guess if you take into account this fact you will get a reasonable answer.
 
In a solenoid there is always a magnetic field in the core. As you increase current, the magnetic field increases causing a changing electric field in the core too. Why is there no energy stored in this created electric field?
 
Electric and magnetic fields are not separate things. They are just math. models to help us describe the interaction between charges, moving (B field) and stationary (E field).

Remember from relativity that the concepts stationary and moving have no meaning.
One observer's B field is another observer's E field.

In fact, these ideas of B and E hark back to the concept of the aether and are are so unsatisfactory now that they are being slowly replaced by a better model (The vector and scalar potentials)
 

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