Questions tagged [magnetics]

Important to inductors, transformers, generators, motors, magnetic fields, inductive heating, magnetic storage, permanent magnets

A changing electrical field produces a magnetic field. These magnetic fields can be used to store and transfer energy, as in an inductor or transformer. Proper mechanical application of the generated magnetic field can apply force or torque to create motion, as in a motor. Reverse application of the same principle can use mechanical action to generate electricity, as in a generator. Information can be stored in magnetic domains, as in a hard disk or magnetic tape.

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What is the difference between the magnetic H field and the B field?

Wikipedia provides a mathematical explanation. Can I get the intuitive one? I'd like to, for example, understand a ferrite datasheet. These usually have graphs of H vs B, and the definition of permeability depends on understanding the relationship…
Phil Frost
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Help with homemade electromagnet

Just for fun, I decided to build what I was hoping would be a relatively powerful electromagnet. I used this copper wire (20 AWG, entire 1 pound spool) and this soft iron core (0.5 in diameter, 6 in length). The total length of the wire is…
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What is the difference between a transformer and a coupled inductor?

Transformers and coupled inductors seem very similar. Is there a difference in construction? Or only in use? This question asks something similar, but the answers don't address my question: Coupled inductor vs an actual transformer?
Stephen Collings
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Do magnetics connectors exist?

Conventional connectors, where the plug and socket have metal parts which touch, suffer from the following problems: Limited mating cycles or expensive plating. Impedance mismatch (relevant for high speed signals only). Lack of isolation. Here's…
Rocketmagnet
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Magnetometer dynamic calibration

I am working on a Magnetometer AK8975 being a part of an IMU. Which seems to be very tricky for me. This chip gives a 3D vector as output describing earth's magnetic field at any place on earth or near it. I tried two types of heading calculation…
Rick2047
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How to calculate air gap in flyback transformer?

I’m designing (or at least trying to design) a flyback converter on LM3478. I chose the EFD20/10/7-3F3 core [1]. Using a PDF from Infineon [2] I calculated that I need a primary winding inductance of about 56µH and a turns ratio of 1:22.125. I have…
urhen
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Why does magnet wire need to be insulated?

What is it about having multiple coils that enables the magnetic field? Why can't I just have one big wire or threaded wire on a motor? Sorry, it's kind of a baby question but I couldn't find the answer.
Isaac
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Why can my bare PCB be magnetized?

I am working on a magnetic sensors design and noticed that my measured magnetic field bias shifts over time. I have studied the bare PCB and measured that it can be magnetized with a strong magnet. I tested two blank (unpopulated PCBS). The first…
Nullified
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Why is inductance (L) proportional with turns-square (N²)?

We start from the Maxwell's Equation $$ \mathbf{\nabla} \times \mathbf{B} = \mu \mathbf{J} + \overbrace{\mu \epsilon \dfrac{\partial \mathbf{E}}{\partial t}}^0. $$ We take surface integration of both sides, for the surface (\$s\$) inside the mean…
hkBattousai
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Ethernet Without Magnetics?

How / can you connect Ethernet devices together without magnetics? How do you wire it up? What sorts of practical limitations are there on doing this? To clarify, I'm not trying to connect two computers here. I'm thinking specifically of creating a…
vicatcu
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Does Shielding "Electrically" shield "Magnetically" too?

I know it sounds like a newbie question but I can't wrap my mind around it. An electromagnetic field is electric + magnetic field. So this means that when shielding an equipment offensively, for example from avoiding causing interference with other…
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Why are reed switches made in glass tubes?

Why are reed switches made in glass tubes? Reed switches sense magnetic fields, and glass is not the only material not affected by a magnetic field. They can use plastic for example. Why are most of them in glass? This question came into my mind…
AHB
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Can a transformer work if the core is not circular?

I am trying to build a transformer to convert 12V AC power to 5V AC. Here is what I have right now: I haven't adjusted the coil ratio yet but I tried it just to see if there would be any output and as a matter of fact there is none. I tested the…
Hadron
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How does this iPhone app measure the power flowing through an AC appliance cord?

My electric utility released an iPhone app called "DTE Insight" which (among other things) measures the amount of power flowing through an appliance's power cord by asking you to hold the cord against a specific part of the iPhone at a specific…
Juffo-Wup
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Tracking rotation with extremely high accuracy

I would like to track the angular position of a fairly slow motorized rotating arm (direct-drive; see illustration below) -- but require angular accuracy of under 0.05°, and similar resolution. As @gbulmer noted in the comments, that is equivalent…
sasha
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