# Tagged Questions

The kind of magic without which all of this wouldn't be possible. This tag should be used for questions about the **physics** of the fields that charged particles create and how these fields interact. It should not be used for all questions involving electromagnetism, that would be everything on ...

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### Looking for boundary sensor

So, I'm looking to build an autonomous robot of a sort and want to know what sensors / MCU packages would be good for dealing with lined boundaries? These would be similar to how dog collars work. ...
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### How to make a power pulsing electromagnet for these requirement?

I have to make an electromagnet for my project. The role of the electromagnet is that I want it to repel i.e. push up so that its hard to press down at that point a ring shaped neodymium magnet from ...
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### Can we draw analogy between em power flow through free space and ac power flow through a transmission line?

Knowing that the free space has a characteristic impedance (which is purely resistive, measured in ohms) I was wondering if I can model the free space as an infinitely long transmission line- ...
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### Ground plane and magnets

I am making a wheel encoder out of a Hall Effect sensor with magnets in a concentric circle on the wheel. The Hall effect sensor is on a 2-layer 9x5mm pcb. I usually fill in the layers by drawing a ...
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### How do construct a electrical resistance tomography apparatus

Im interested in constructing an electrical resistive tomography setup to image underground structures. While I somewhat understand the principle, I have found limited information on design and ...
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### How can I find the stored energy in a 2d triangle that has a different electric potential at each point?

I am writing a FEM solver for a project. I need to calculate the total energy stored in my mesh so that I can compute the capacitance of the solution. So obviously I have to loop through all the ...
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### Salient Pole Machine Inductances

While dealing with a salient pole machine, the stator-rotor inductances get modified through the addition of an extra term which is multiplied with the cosine of twice the electrical angle of ...
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### Average flux density in a standard pair of headphones? (AC fields only)

I don't have a teslameter to measure it, so can someone with expertise give an approximate as to what the flux density may be next to one speaker elements in a normal pair of studio earphones (not ...
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### Long distance interaction DC electromagnet (solenoid)

I want to construct a DC electromagnet (solenoid) to interact in distance i.e to attract a steel ball 100gr, 30mm in diameter, placed 10cm away (vertically) from electromagnet. This system will use to ...
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### Detecting volume of metal along a straight line

I am looking into creating a simple interactive demonstration for MRI scanning which is a device which will detect the internal configuration of a solid block of LEGOs. The idea is to have a fixed ...
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### Reversing polarity for electromagnets

I'm fairly new to electronics - software engineer by trade. I get the basic parts, but have no experience with circuit design or such. I picked up a neat WWII era wind speed and direction gauge set ...