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Questions tagged [electromagnetism]

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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37 views

How can a magnetic circuit with an airgap have a higher e.m.f in the secondary coil than the same circuit without the air gap?

I have a magnetic circuit with the same configuration as in the image, the primary coil has 203 turns and the secondary has 406 turns, how do I get a higher eletromotive force when there is an air gap ...
3
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1answer
51 views

Drift current in PN Junction

Ok guys, first of all thanks for your support and your help, I can't understand how the drift current work, let's say that we have this junction By the definition of the drift current we can ...
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1answer
47 views

Can a coil gun be made with a boost converter instead of caps?

So I’ve been starting to build a coilgun, and I find most designs either have capacitors or are just really bad. But could a high-voltage boost converter (40000v) and a momentary switch not be used to ...
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1answer
34 views

Odd step in derivation of phasor Telegrapher's equations

In the derivation of the phasor form of the Telegrapher's equations (in "Fundamentals of Applied Electromagentics" by Ulaby), there is a step I'm not following: When going between eq. 2.16 and eq. 2....
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4answers
104 views

Does the EM radiation from AC power lines propagate through air or is it fixed around the line?

Because of the AC current flow, there is a changing magnetic field around the conductor, that in turn induces a changing electric field and vice versa But does the EM radiation get "loose" from the ...
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2answers
58 views

Can you turn two inductively coupled conductors into a transformer?

So I'm working on a school project, and to be honest. Don't know a lot about electromagnetism. I want to make a wireless charging station that could be plugged into the outlet. Of course I don't want ...
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0answers
75 views

How many amps of current should a 120kg lifting magnet require?

I've recently purchased a 12v electromagnet capable of lifting 120 kg's which I have been told requires 0.43 amps of current to reach be able to lift 120 kg's. However when I supplied this to the ...
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2answers
35 views

Area of iron core to lift a certain amount of weigh(magnet/solenoid)?

I've been wondering and testing selfmade magnets by wrapping iron with wires and applying a voltage to it which makes it a bit magnetic. I've been looking around the internet and can't seem to find ...
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0answers
37 views

System of multiple conductors: image method

The problem statement, all variables and given/known data The following figure represent the traversal cut of a system with two cylindrical equal conductors of radius r0 length l at a distance d ...
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0answers
67 views

Intuition behind transit angle of a klystron

What I understand is that the electrons get attracted to the anode and during their passage through the buncher gap, they regroup into bunches due to differing potentials imposed on different ...
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1answer
116 views

What is the purpose of perpendicular “smaller” magnets in between the main magnets in a rotor of a motor? had never seen this before. Do they help?

I am trying to build my own generator at home for fun, I saw on a video in youtube https://www.youtube.com/watch?v=YsSm65DAcCg where the guy placed smaller magnets in between the main magnets of the ...
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1answer
61 views

how to pick the low carbon steel scrap from ms trolley using electromagnet

I want to pick the low carbon steel scrap using the electromagnet from the ms trolley in which the low carbon steel scrap is present? how to pick the scrap without effecting the ms trolley(95kgs), how ...
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4answers
171 views

EMF Induced Between Parallel Conductors

If two conductors (A and B), separated by a distance R, are parallel for a length ℓ and conductor B has an AC current flowing through it (I), what would be the equation to calculate the EMF (voltage) ...
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0answers
53 views

Can an inductor couple energy to a speaker through a PCB?

I am designing a circuit where I have, among other things, an AC/DC buck converter (Iout_max = 250mA) and a transducer. I am drawing the PCB layout and I have the following situation: The inductor ...
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0answers
27 views

Linear induction motor back plate

In a single-sided linear induction motor, there needs to be an iron back plate behind the reaction plate(of Aluminium). Is it necessary to generate force and if it is necessary what is the reason?
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0answers
33 views

Move an object vertically and rotate it on top of another object

Setup - a 4x4 bi-polar electro-magnets tied to a surface (see first image). There are 2 objects: one which has 1 face with the electro-magnets and another that has 2 right angled faces (each face has ...
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1answer
40 views

Unit conversion: dBμV to dBm, including measured frequency

I'd like to ask for help with conversion of measured voltage V=10dBμV to dBm units. Voltage is measured on frequency ...
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1answer
92 views

In an induction cooktop, what happens to the coils resistance when there is no pot? Does it vary between pots? How does the appliance respond?

An induction cooktop (or an induction rice cooker) uses a copper coil with a high-frequency alternating current going though. The magnetic flux heats any iron-alloy pot placed above. But what ...
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1answer
48 views

Which material is considered non linear communication channel?

Communication channels as far I have seen(Air and conductors) are modeled as Linear systems. Was wondering if there are mediums/materials that make the channel nonlinear? For example, if channel is ...
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0answers
37 views

Metallic Waveguide Boundary

I've been studying TE and TM modes on waveguides for microwave frequencies. It basically consists on applying Maxwell equations on a rectangular metallic cavity, with infinite length on \$z\$ ...
2
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3answers
103 views

Transmission Line Effects

My question has to do with the rule of thumb we generally use when dealing with transmission lines. We say that if the length of the line is 10% or less of the wavelength, we could neglect the ...
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0answers
21 views

How to use a HDD read/write head to read micro-magnetic fields?

Someone can tell me if Is possible to create an external circuit using the HDD Head Read/Write like a sensor, to read micro-magnetic fields? Can I remove the HDD head and control this?
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23 views

Open and short circuit voltage in magneto primary coil

As illustrated in figure 1 and 2, I measured the voltage across the primary coil of an aircraft high-tension magneto in an open circuit condition (figure 1) and short circuit condition (figure 2). The ...
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3answers
238 views

Does the phone transmit waves? [closed]

In a cellular connection, How much is power density (in W/m2 or mW/cm2) of the RF energy from the phone to the tower? If not possible in above units then can I know in dbm ? My phone has: Head SAR: ...
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1answer
50 views

Voltage (and possible resistor) required for electromagnet

I have a small electromagnet which moves a lever (it's a part from a larger device). I'm not sure of the supply voltage but other parts of the device required 20V. The resistance of the electromagnet ...
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1answer
42 views

relay control with network and sms with main controller [closed]

I need this project for a melting plant. There must be two relays in the control (connected to the device), so if one of them is in trouble, another will work to disconnect. In the (current check) ...
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3answers
2k views

How to transfer energy generated from electromagnetic induction to a USB port?

For a school project, I'm creating a shake-powered phone power bank that will generate current similarly to a Faraday flashlight, which will in turn power a usb port. A simple enough concept. Now to ...
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1answer
70 views

Effect on coil of two magnets moving in opposite direction

There is a coil of wire making up a closed circuit and two magnets. What would the effect be on the circuit if we simultaneously moved one magnet towards the coil and the other magnet away from the ...
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0answers
31 views

Alternate formulation for the Neumann formula

I'm currently learning about the Neumann formula for the calculation of the mutual inductance between thin current filaments. However, for future purposes I want to find an alternative formulation of ...
3
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3answers
103 views

How feasible is it to localize a robot based on EM beacon?

I am designing a little tabletop robot with a very simple goal of keeping track of where it is on the table as he traverses it. This, as it turns out, is a lot more difficult than I imagined. All the ...
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1answer
40 views

Reasons and assumptions behind the use of per unit length quantities in the telegraph equations

I am working out the derivations of the telegraph equations of a transmission line $$\begin{gathered} \frac{{\partial V}}{{\partial x}} = - L\frac{{\partial I}}{{\partial t}} - RI \hfill \\ \...
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1answer
104 views

Discharging a capacitor quicker, using an exterior time varying magnetic field?

I was analyzing the possibility of varying an exterior magnetic field, that's aligned in direction with the magnetic field produced by the displacement currents(both parallel in the same plane) shown ...
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1answer
64 views

Inductor Coupling Question

I want to prove that a voltage signal I apply in the primary of an ideal transformer(or 2 coupled coils) will produce the same voltage signal in the secondary, e.g. a square wave(+- V) in the primary ...
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1answer
98 views

Why was the term electromotive “force” used instead of voltage or potential difference in original Faraday's law? [closed]

Faraday's law is always given as: ' I always wondered why a phenomenon which is totally "electrical" and electromagnetic has anything to do with a terminology from mechanics like "force". If there ...
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1answer
59 views

If counter-emf is zero, why is COE violated?

I've been modeling this thought experiment a for a while now: If in a electromagnetic system, the induced emf wasn't opposing the change, but increasing it, we're getting energy from nowhere, that ...
6
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1answer
108 views

Sparks on grounded metal bodies on lighting strikes in the nearby (two miles)

I have a strange phenomenon in our mountain cabin, on the Italian alps: lightning strike on the nearby (not so near: < 2 miles) causes audible / visible sparks on: electric / fire wood water ...
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0answers
72 views

Electromagnet: multiple thin wire windings instead of one of thick?

I'm designing a solenoid-based actuator, after doing calculations using this website, i found the proper wire thickness needed to get right force at a given voltage. The problem is, here, where i live,...
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0answers
28 views

How to compute the least overshoot Voltage used by schottky rectifier?

I have a schottky rectifier, it's 11DQ10. I know the Max. Working Peak Reverse Voltage is 100V Vrrm? If i give it a singal which is a Damping pulse, the first peak maybe over 100V, but the second ...
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1answer
48 views

Calculating the magnetic flux density in cylandrical coordinates near a neodymium disc magnet

I am looking for an analysis of a disc magnet, I have heard there are 2D analaysis and 3D. Could someone point me in the right direction of a paper or some academic text on the matter. I don't mind ...
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6answers
115 views

why does a step up transformer cause lower currents?

The usual answer I hear is because power needs to be conserved, but I dont find that answer satisfying. Normally if I were to double a supply voltage in a circuit, then I would expect twice the ...
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0answers
42 views

an arc at what amperage/AC voltage would be at a sufficient temperature to melt most common metals?

I have come across a video recently (link below) that uses two microwave transformers to step down voltage from a wall outlet to be used to melt metal as an electric arc furnace. However, he neglected ...
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1answer
55 views

dangers of building electrical arc furnace

I am currently rewinding 2 microwave transformers to create an electrical arc furnace. I have taken the secondary coils out of each transformer and am planning on winding new ones. In theory the ...
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1answer
35 views

Cable having a coil like loop

Is this ok? Or should we avoid using a loop like this 3 phase cables connecting from an isolater to terminals. The cables have a coil like loop in them.. a single loop to make it less stressed ...
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2answers
115 views

What effect would a hydrogen bomb detonated at high enough altitude have on the power grid and solid state electronics?

After reading several dozen reports on EMP effects of nuclear explosions and viewing archived government footage of nuclear weapons testing I have come up empty handed. As for example let us assume ...
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1answer
71 views

Why does having magnetic material in the middle of a stator help generate a current?

It seems unintuitive to me why putting a stationary hunk or iron or neodynium in the middle of a copper coil generator would increase its conductivity, because the metal could act as its own ...
2
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1answer
107 views

I don't understand the windings inside my power drill. [closed]

I was curious about how my power drill worked and I disassembled it. I understand the general principles at work here but I don't understand why the winding is set up this way. I assume running ...
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2answers
53 views

Air core solenoid Melting when given 3amps with neodymium magnets as core

I'm currently using magnets and ferrofluid in an art project. I'm not experienced with electrical engineering but maybe that will be obvious after reading this question. I'm currently using this air ...
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1answer
31 views

Field decay of magnetic dipole

1) What is the decay of the magnetic field of a magnetic dipole? It can be modelled as a ciruclar current with infinitesimal small radius. The decay of a current carrying wire can be easily ...
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4answers
232 views

Magnetic field strength and flux density from hysteresis curve

I am trying to measure the magnetic hysteresis curve of a toroidal nanocrystalline ferromagnetic transformer core made of Nanoperm (datasheet linked) using the following circuit. Each of the windings ...
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1answer
28 views

Xbee pro s2c 2.4 ghz 10dbi Antenna and its effect

Just wondreing how to increase the range/distance of communication between two xbee modules operating in API mode, we are considering to replace the 2.4 ghz antenna of 5dbi gain with 10dbi high gain ...