# Questions tagged [magnetic-flux]

The sum normal component of a magnetic field passing through a surface.

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### Logic gate circuit to close when sensor signal turns ON and then OFF, but must ignore another ON?

I am trying to put a permanent magnet in a transformer between both coils, so that the transformer can utilize the flux from the permanent magnet by guiding its flux periodically. We have one primary ...
28 views

### EMP Halbach Array

Let's say I have a horizontal facing halbach array with equal north and south poles aligned one after the other, and a large circular gap in between them. If I fire an EMP gun through it, wouldn't the ...
18 views

### Bi polar pulse magnetizer controlled by arduino

Hello, I am trying to make a bipolar pulse magnetiser based on the pulse magnetizer design on instructables. I attached my circuit design as image. g1 and g2 terminals of the thyristors will be ...
98 views

### DC through an inductor

I get that the frequency is zero hence the voltage is consequently zero according to the the equations, but any current through a conductor should produce a magnetic field. I also understand that ...
944 views

### What happens if the secondary of an ordinary transformer is left open?

Let's consider a transformer. The ideal transformer equation is: $$\frac{V_1}{V_2} = \frac{I_2}{I_1}$$ Suppose the secondary is open (that means $I_2 = 0$): it will result $I_1 = 0$. How is this ...
41 views

### Does transformer's flux (due to load) need to obey Faraday's law

I believe I have a good understanding of a transformer. But I may have a misunderstanding somewhere that is leading to absurd conclusions. My overall understanding If we ignore all losses and look at ...
76 views

### Electromanetics question

Question : An infinitely long, very thin cylindrical conducting tube of radius b carries a uniform surface current Js = azJs(A/m). Find B everywhere. When r<b, it says that "In condition flux ...
37 views

### Why am I getting different flux densities?

I am trying to find the flux density at the top of the core. The current is known to be 2.5 A, the relative permeability of the core is known to be 800 H/m, and the flux is known to be 0.005 Wb. ...
67 views

### Do I need a diode to protect my ESP32 from a connected relay?

My ESP32 is controlling a relay which I switch on for 500ms (controlled through the internet). Do I need a diode to protect my ESP32 from voltage spikes when the magnetic flux collapses? I'm using ...
35 views

### Rotating magnetic field discrepancy

This may be a noob question Lets consider a balanced 3 phase supply namely \begin{align} R&= V \sin(x)\\ Y&= V \sin(x-120)\\ B&= V \sin(x+120) \end{align} At a neutral point we would ...
40 views

### why should we define "the magnetic flux is the dot product of the magnetic field and the plane area , instead of perimeter of the plane

When a uniform magnetic field $\mathbf B$ passes a plane at any angle, the magnetic flux $\phi_B$ is the dot product of the magnetic field $\mathbf B$ and the plane area $\mathbf{a}$,that is ,\...
64 views

### What is meant by AT/cm in transformer?

In a problem related to transformer loss I have found a line "AT/cm for a flux density of 1.2 Wb/m^2 in iron to be 5" I've searched in google for 30 minutes about what is AT and how it is related to ...
93 views

### How does magnetic flux affects the speed of a DC motor

I'm doing a high school physics project where we need to investigate the relationship between the speed and magnetic flux of a DC motor. We built a simple DC motor which basically looks like this, ...
177 views

### What happens to parts of induction cooker magnetic field not covered with the pan?

An induction cooker works like this. There's a flat coil of wire under the cooker surface which is connected to a source of high frequency AC and it produces an oscillating magnetic field with field ...
56 views

### Variable field magnet motor?

See the video in the following link: https://www.youtube.com/watch?v=olnXy-J48SY "Variable field magnet motor" How does this work and is it actually efficient?
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### Why exactly does peaking of magnetization current occur in a transformer?

Initially assuming that the input current is sinusoidal. In a practical transformer, flux $\phi$ produced in the primary is not linearly proportional to the current $I$ through it. Due to ...
75 views

### Magnetic flux induced in toroidal core and conductor position

I was just reading Electric Power Engineering by Elgerd when I came across these statements about flux I couldn't fully understand: "By experiment, we can confirm a most interesting ...
22 views

### Radio frequency coil for homogeneous B field over area

Are there any possibilities of creating a coil which would function at high frequency (MHz range , maybe up to a few GHz) and which would give me a B field that could be used to penetrate a certain ...
40 views

### Is it possible to get Flux in a magnetic circuit with zero mmf?

From an Example that I stumbled upon on A.E. Fitzgerald's book on electric Machines. He assumed that there is flux in a circuit with zero mmf. Which I find very confusing. I would appreciate it if ...
122 views

### How to design an inductor which consists of four separate windings in the same core?

I need to design an inductor such that there will be four separate windings at the input side (each input is coming from a different DC-DC converter) then these four windings are combined at the ...
326 views

### Why are the poles of the stator and rotor taken differently in the picture below?

The rotor and stator in the picture below have the same orientation of flux lines yet the are taken as opposite that is flux lines leaving the stator is taken as a South Pole while flux lines leaving ...
125 views

### Calculation of magnetic field saturation inside coil core

I want to try to make an electromagnet, but I don't have soft-iron available. I've read that ferrite MnZn are suitable as soft-iron to create a high efficiency magnets with the inconvenient of lower ...
61 views

### Magnetic force as a function of PWM frequency

Consider an experiement with a DC source feeding an coil with a constant DC current I. The coil with an iron core attracts a magnetic plate with mass m with force F. The force F is higher than Fm and ...
46 views

### How to calculate the emf with flux density given instead of flux

So I have the following question What is the emf in a coil of 2000 turns and c-s area 10cm2 when a flux density of 0.4T density in it is reversed, i.e. in a time of 20ms. Also what would be the the ...
196 views

### Can we use the Halbach array configuration in an electromagnet?

I tried asking this question in several forums but didn't find any answers as i expected. It's very hard to find information about halbach array in google, especially in the electromagnetic field. We ...
41 views

### How do I determine what magnet to use at a specific distance for a reed switch?

I have a reed switch that shows a 10AT to 15AT operate range on the data sheet. I need to determine if specific magnets will fire the switch, and at what distance. The magnets I'm looking at though, ...
68 views

### Why does the V/Hz ratio of a motor affect the magnetic field strength?

When the frequency is increased whilst keeping the voltage constant, the magnetic field strength is going to weaken... I don't understand why and what actually happens that causes the field strength ...
101 views

### Inductance of a single conductor

Which is the correct expression for the inductance of a single conductor? I see 2 different formulaes for the same in different sources. Formula 1. Ref: https://www.eeweb.com/tools/wire-inductance ...
131 views

### From a flux point of view, how can we explain that the equivalent inductance is half when identical inductors are connected in parallel?

The equivalent inductance of 2 identical inductance connected in parallel ( ignoring mutual coupling) is half of the orginal . This result is usually derived from the argument of identical voltage ...
30 views

### Does magnetic flux depend on the orientation of the ferromagnetic rotor?

I have attached a picture of a reluctance motor setup. When I turn on the AC source, magnetic flux lines will build up. My question is, will the magnetic flux will be a function of the angle turned ...
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### Mean Free Path of Magnetic Core

I don't understand how they got the mean free paths (ls) of each leg. I know that I should be calculating the longest + the shortest paths and divide them by two, but I don't know HOW I should be ...
41 views

### Which capacitor in series with resistor circuit to reduce remanence effects of transformer?

The "Comparative Analysis of Mitigation Techniques for Inrush Current of Transformer" mentions "Pre-insertions resistor with capacitor method" as an inrush mitigation technique: When circuit ...
147 views

### Pancake Coil Magnetic Field Strength

I am trying to measure the magnetic field strength of a pancake (flat) coil. I know the turns, inner radius, current, and frequency from an AC input and am trying to measure the magnetic flux so I can ...
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### What's the name of the force that opposes the movement of magnet trough a coil?

I am trying to make an experiment that looks like this: I am using this source https://physicshandson.wordpress.com/2019/02/04/damped-oscillations-in-mechanics-and-electromagnetic-induction/ as a ...
56 views

### Increase emf received from a coil without changing flux source

I have a situation where I'm trying to increase the amount of power received by a coil. To my understanding, I can increase the emf (voltage) by doing one of 4 things: Increase the number of coils (\\$...
105 views

### Field Flux control and Speed Of DC motor

I was studying electromagnetism and I tried to link with working of DC motors. For the speed control of DC motor - The Flux of DC motor is reduced to increase the speed above rated speed. I ...
264 views

### Electrical equivalence and Difference between Flux and Torque in AC motors

For AC motors, Synchronous and Asynchronous ones, are these two linked together or different quantities, namely magnetic flux and torque? Also if I want to measure these quantities electrically then ...
53 views

### Infinitely linear torque with current in motor?

I'm trying to find the maximum current my brushless DC motor can handle. If I can keep the coils and cabling cool (in a freezer right now), is there any other fundamental limit I may hit such as ...
63 views

### Magnetic Monopoles and Magnetic Current Densities

I see that in electronic engineering the Maxwell equations are written with also some terms which represent the magnetic charge and the magnetic current densities. I was told they are inserted only to ...
212 views

### Can a change in magnetic field change the impedance of a coil

I kept a coil in a linearly increasing magnetic field and calculated the impedance by measuring the induced current and voltage. When the maximum value of magnetic field was reduced (while keeping ...
150 views

### Is a coil FM transmitter frequency affected by my body static?

I've built this coil FM transmitter following these guides which are essentially the same: https://maker.pro/custom/tutorial/how-to-make-an-fm-transmitter https://www.instructables.com/id/The-...
68 views

### Leakage Inductance Coaxial Cable

I do not understand how a particular parasitic effect is model. I have read that on a coaxial cable there is a problem due to the fact that the external conductor's magnetic field crosses the air ...
63 views

### Is it possible to determine a low power isolation transformer maximum output current?

I have a transformer (no codes) 240vac to 12vac this is easy enough to determine but what about the maximum current? 1) I could load it until the voltage drops but to what exactly? 2) Is there any ...
26 views

### Confusion regarding the right hand thumb rule

I am confused regarding the use of the right hand thumb rule . There is two use cases for this rule : 1- The first when the thumb points in the direction of the current the fingers points in the ...
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### Shape of a core for use in a solenoid

I am currently designing an electromagnetic accelerator meant to accelerate a spherical nickel-plated NdFeB (neodymium) projectile along a circular tube, in a similar manner to a particle accelerator. ...
188 views

### Parasitic Inductance

when we say that in a wire there is a parasitic inductance, what is its cause? Is it the skin effect of the wire, the magnetic flux (generated by the current) through the surface of the total circuit ...
131 views

### How do I convert the units of a moving magnetic field to volts?

Copper wire wrapped around an iron core produces current when a strong magnet is moved in its vicinity. I gather the "magnet movement" part is expressed in units of "weber" (kg⋅m2⋅s−2⋅A−1) or perhaps ...
163 views

### What causes the residual magnetic flux when the current is zero in an inductor hysteresis curve?

An inductor with hysteresis has the following current versus flux curve: I marked the point in red where the current is reduced to zero but there is still flux on the above curve. What really causes ...