What is Back EMF?
The OP seems to have mixed up some inductors and capacitors concepts.
For inductors we don't consider the electric field, which is for capacitors. We consider her twin/mirror sister, the magnetic field.
For an inductor, say, if you apply a voltage across it, current increases exponentially and after some time, to an almost steady current (Appendix A).
For this almost steady current flowing, there is a magnet field built up, which stores energy, and let us call it magnetic energy.
Now the fun part:
If at this time, you try to switch off the voltage applied to the inductor, the almost steady current can no longer flow, so it would try desperately to find an alternative current path to flow. Why so desperate? This is because the stored magnetic energy cannot disappear suddenly (Note 1), otherwise the Law of Conversation of Energy would be violated (and Mother Nature would be very angry, and would not allow this to happen! :)).
Note 1 - The energy built up is equal to ½ * L * I² (Appendix B), so it is proportional to current I. In other words, if I stops suddenly to become zero, it means energy suddenly disappear to nothing, and this against the Law of Nature. However, it is OK for this magnetic energy to convert to another form of energy, say heat energy.
Anyway, if you don't provide an alternative current flowing path using say, an "flyback" diode, which allows the flowing current to continue flowing "in the same original direction" , and dissipating the originally stored energy in the magnetic field as heat energy at the diode, which gets hot.
If there is no flyback diode, Mother Nature will create an alternative current path for the human, as described below.
A big voltage potential, called Back EMF (ElectroMagnetic Force) will let the flowing current to continue to flow, by ionizing the nearby air to become sort of a electricity conductor (actually a poor conductor, or high resistance), and the otherwise no where to go current would happily go through.
Since the ionized air is not very conductive, so the back EMF ("back" means "fighting back" (Note 2) the force to stop current flowing) must be very high, sometimes thousands of volts, to break the air molecules into ions, for the current to flow.
Note 2 - The idea of "fighting back" is a general thing, similar to Newton's Third Law: "Action is equal to (fighting back) reaction". Lenz discovered this phenomenon a couple of centuries ago. BTW, the Back EMF concept as explained here, using a simple current switch and a flyback diode is only one of the many specific cases of a general thing. There are many other specific cases, say, in transformers and motors, that also find back EMF.
So you see the "sparks", which are the poor little guys, knocked out along the way, by the current rushing in a big hurry.
Now energy has converted from magnetic to heat, thus conserved.
Universe is in harmony, no scary Big Bang would happen again.
Mother Nature is happy and goes back to sleep, until another naughty human again switches off some flowing current which has no where to go, and the fun repeats ...
End of Back EMF story.
(1) Electricity and Magnetism Concepts - HyperPhysics, Dept of Physics and Astronomy, Georgia State University
(2) Back EMF - Wikipedia
(3) Lenz's law - Wikipedia
(4) Newton's Third Law of Motion - The Physics Classroom
(5) Electromagnetic Interference (EMI)
(6) Electromagnetic Induction (EMI)
(7) A Portrait of the Back EMF as a Wavelet - Rpi.org.forum 2019jan10
(8) Back EMF Suppression (For Magnetic Door Locks) - Progeny
Appendix A - Inductor current, magnetic field, and magnetic energy
Appendix B - Magnetic Energy
Appendix C - EMI (Electromagnetic Interference) in IC and How to reduce them
Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction.
The disturbance may degrade the performance of the circuit or even stop it from functioning.
In the case of a data path, these effects can range from an increase in error rate to a total loss of the data.
Both man-made and natural sources generate changing electrical currents and voltages that can cause EMI: ignition systems, cellular network of mobile phones, lightning, solar flares, and auroras (northern/southern lights).
EMI frequently affects AM radios. It can also affect mobile phones, FM radios, and televisions, as well as observations for radio astronomy and atmospheric science.
EMI in integrated circuits
Integrated circuits are often a source of EMI, but they must usually couple their energy to larger objects such as heatsinks, circuit board planes and cables to radiate significantly.
On integrated circuits, important means of reducing EMI are:
Use of bypass or decoupling capacitors on each active device (connected across the power supply, as close to the device as possible),
Rise time control of high-speed signals using series resistors, and
IC power supply pin filtering.
Shielding is usually a last resort after other techniques have failed, because of the added expense of shielding components such as conductive gaskets.
Appendix D - Displaying the waveform of a back EMF voltage wavelet
Two years ago I used an electromagnetic buzzer to switch on/off the current in the buzzer inductor coil, attracting/releasing the spring flap current making/breaking contact. There is no flyback diode. I also tried using relays and solenoids without flyback diode. I used a scope to display the current pulse, as shown below.
Ref: A Portrait of the Back EMF as a Wavelet - Rpi.org.forum 2019jan10