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 ...
6
votes
1answer
210 views
Faraday Cage - Detecting one
I am looking for a cheap and easy way of creating a small electronic device that is capable of detecting whether or not it is inside a Farraday Cage.
Hopefully, without an external sensor/emittor.
0
votes
0answers
192 views
Electromagnetic radiation from specific monitors [closed]
I'm concerned about the health impact from EMF produced by home/office appliances. In particular I would like to know if somebody measured the Electromagnetic radiation of any of the following ...
5
votes
4answers
231 views
M.S. Math to Engineering Ph.D : Mathematics in Electrical Engineering
I have two Bachelor's degrees. One is electrical engineering and the other one is mathematics. I am studying mathematics (partial differential equations) in the graduate school (Master course) now. ...
1
vote
1answer
258 views
How to determine the force of a solenoid based on inductance
I'm looking to potentially build my own small solenoids, I thought perhaps that I could take an Air core inductor, a spring, piece of plastic, and conductive core and build my own. Is there a way to ...
0
votes
1answer
317 views
Multi-tap transformer current handling capability
I have a transformer with a single secondary winding but with multiple taps, as shown in the image.
It is rated at 4A @ 24V (96VA).
Does this mean that at lower voltages (16V and 8V) it will be able ...
2
votes
1answer
115 views
Automobile ignition coil (spark coil)
Question: How is this possible to get 1:1000 electric potential scale while primary/secondary loop scale is only about 1:100?
2
votes
1answer
173 views
Controlling temperature of a water bath with induction plate
I am thinking of building a sous-vide cooker using some kind of prebuild heater, controled via an AVR and temperature sensor like the LM35. There are a lot of references around using rice cookers, ...
3
votes
3answers
214 views
How is electricity typically generated?
I am a pure physics guy, so I understand the fundamental processes behind the generation of electricity, but I'd like to know how to apply it. I was wondering what kind of methods were used in the ...
8
votes
1answer
170 views
What is the dielectric constant of a fly?
Kind of a random question, It has been a topic of debate in my lab. I guess the more specific question is: what materials is a fly's body made out of, and what are their dielectric properties?
0
votes
1answer
217 views
Building a coil for galvo motor
I'm building myown galvo motors and for that I need some coils that I'll have to build myself to fit into the dimensions I need.
Is there any technique for winding the wire or is it just straight ...
4
votes
2answers
193 views
Why don't my coil work?
I disassembled my old Niko RC car today. Thought I could play around with the parts.
But what I can't seem to understand is the coil. The powersource of the rc car is a 7.2v NiCd 620mAh battery. And ...
0
votes
2answers
113 views
How do I get this spool to work?
I have this spool (image) and did some testing with a multimeter before I disassembled it. It's working range was [-3.3v,0v,3.3v]. When I tested it by just applying the battery after disassembly ...
2
votes
2answers
325 views
Magnetic door lock
I'm looking at buying an AEM10010 magnetic door lock (see page 4 of datasheet), but can't figure out how they're driven. The datasheet doesn't say anything about how to connect them, nor does it ...
5
votes
5answers
300 views
Calculating resistance in decibel
In EMC there is an equation for charactristic impedance (If I am not wrong) that is defined as:
$$Z_w = \frac{E}{H}$$
As you know \$E\$ is expressed in Volts and \$H\$ as Ampers.
I had the exam ...
2
votes
2answers
142 views
Stepper motor phase
I have a question related to stepper motors.
What does the "phase" of a stepper motor mean? I mean when we say that a stepper motor is a 2 phase stepper motor or a 4 phase stepper motor, what does it ...
16
votes
3answers
923 views
Why aren't solenoid/electromagnet windings insulated?
This has been bugging me for a long time. Take this video for example.
I have always thought that electricity will take the shortest path. When the electromagnet's windings are uninsulated, it seems ...
3
votes
2answers
215 views
Sending data over a magnetic field
I need to find a way to trigger this Hall Effect Sensor with a non-permanent magnet. Does anyone know if an inductor's magnetic field would be strong enough? Or am I going to have to build an ...
1
vote
3answers
522 views
Why voltage lags by 90° from magnetic flux?
I was not sure if I should write it here or on Physics board, but I will give a try.
As I understood current (generally emf) can be generated in a system by varying magnetic flux.
For example, let's ...
5
votes
1answer
195 views
Best way to affect a compass in 2 meter distance
Visitors of two public exhibitions A and B are equipped with compasses.
Exhibition A:
I want to guide these visitors along a certain path throughout the exhibition by "overriding" the earth magnetic ...
1
vote
0answers
106 views
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 ...
3
votes
2answers
248 views
Why does the ISDN S0-Bus require terminating resistors?
It is a well-known fact that ISDN S0-Bus must be terminated with 100ohm resistors to match the transmission line. This is the case even for everyday household installation with cable runs shorter than ...
1
vote
2answers
904 views
Solenoid Alternative?
I wanted to use solenoids in previous projects and have been let down by the fact that I can't find them here in Egypt. Plus they are a bit expensive. My question is: is there an alternative that it ...
4
votes
1answer
98 views
Fine-grained sensing of distance between two permanent magnets
(disclaimer: bit of an electronics newbie here)
I have a bunch of little magnet ball-bearings that I was playing around with the other day. I formed them into a strand, then fixed both ends leaving ...
3
votes
1answer
660 views
Any open tool for graph plotting for determining PID tuning parameters?
I have gone through several PID implementations and its tuning tutorials, documents and all. The Best tuning tutorial was PID-without-a-PhD.pdf . But has not been of much help. I can say it works ...
1
vote
1answer
165 views
How can I describe the behavior of an inductor without reference to a magnet?
In class we have been given an exercise to simulate capacitance, inductance, and resistance without reference to - well, without refernece to much of anything. The resistor is straightforward, ...
1
vote
1answer
120 views
Help with connecting electromagnet to dimmer
I have an electromagnetic powered off a AA battery. Is there some kind of dimmer switch or similar item that would allow me to control the amount of power going to the electromagnet?
7
votes
2answers
297 views
Using the audio input port as a voltmeter
I'm a physics undergraduate currently studying electromagnetism. I have no experience at all with playing with electronics. I'm trying to see the effect of a changing magnetic field on a closed ...
5
votes
3answers
1k views
Putting far more mechanical energy into a generator than its electrical load
Funny how I was pondering about this question for a long part of the day yesterday, and today I was at stackoverflow and in the box with the featured questions from other SE sites this very related ...
9
votes
1answer
987 views
How to shield microcontroller from electromagnetic interference
I'm working with high voltage circuit (2.1 kV for defibrillator capacitor testing) and I'm controlling power supply with arduino, reading required information from laptop using serial interface. Most ...
4
votes
2answers
279 views
Will a 3 phase induction generator fight its own rotation?
So in a 3 phase induction generator with coils for the stator and magnets for on the rotor, I am wondering if the the current induced in the coils would create a magnetic field that would oppose the ...
0
votes
2answers
685 views
How to turn an electromagnet on and off?
I need to control an electromagnet as follows:
I need to switch it on/off every T seconds, where T is around 1 second.
I need to be able to change that time, using something like a potentiometer.
...
3
votes
3answers
141 views
A few questions regarding B/E-fields in practical circuitry
I have been trying a few learning resources to help unlearn some of the notions that electrons flow through as energy.
Chiefly this resource is what I have used:
Amasci - IN A SIMPLE CIRCUIT, WHERE ...
0
votes
1answer
133 views
Mixing wavelengths to produce light? [closed]
It's a mixed part question:
1) Is there any way to add 2 wavelengths outside of the visible spectrum to create a wavelength in the visible spectrum?
2) If this is possible, would those wavelengths be ...
1
vote
3answers
487 views
Controlling Electromagnet Via USB
I need to control an electromagnet via USB with an android phone, to make a small educational project.
I know how to write the software, but how can I control an electromagnet via USB?
Via an USB ...
1
vote
1answer
351 views
Do diamagnetic material exhibit induction?
Silly question perhaps, but do metals with the property of diamagnetism also exhibit inductance? Would a fluctuating magnetic field induce a current in a diamagnetic metal?
5
votes
4answers
2k views
Do electromagnetic shielding stickers do anything?
I recently bought some cellphone accessories, and as a free gift, the merchant gave me a "24K gold plating electromagnetic shielding sticker", whose instructions are all in Chinese, but I guess you're ...
3
votes
1answer
203 views
Good resources/books for electromagnetics and other advanced concepts
I'm looking for some good resource that teaches the fundamental concepts behind electronics. I'm not looking for a beginner book. I'm already in the final year of my Electronics and Telecommunication ...
1
vote
2answers
188 views
Can the coil in a magnetic field be replaced by a copper mesh?
From theory, I remember that EMF induced is a function of the rate of change of magnetic flux. A generator is typically a changing magnetic field applied to a bunch of diamagnetic wires wound closely ...
4
votes
4answers
218 views
Will a faster rate of change of flux improve electricity generation?
From what I remember about electricity generation, a varying magnetic field is used, either the magnetic field or the coil moves to generate electricity.
e = dB/dT
where
e = voltage induced
B = ...
2
votes
1answer
241 views
Generating Strong Electric Fields
What is the best way of generating strong, steady, electric fields (E) using the tools and voltages available to the home hobbyist? Is it better to using electrostatic sources like a Van de Graaff ...
6
votes
4answers
294 views
Is it possible to record a range of radio frequencies in one go?
I am wondering if the following is theoretically possible:
The device can record say 1 hour of electromagnetic wave/radio signals today, and in the future recreate/replay that, so people can listen ...
4
votes
1answer
261 views
What use is the copper foil between the primary and secondary windings of a transformer?
I took apart a small transformer. It is of shell construction type. Beneath the primary windings, I found a strip of (floating) copper foil wrapped around the secondary windings. Of course there is ...
5
votes
3answers
513 views
Inductors & magnet - no vibration
I was trying to make a device which can vibrate - so I took inductor, some 220uH 22uH, put 12V pulsed current through it (~10Hz), and put neodymium magnet - I was expecting to feel 10Hz vibration of a ...
0
votes
2answers
179 views
Electromagnet force
If connect a battery to an electromagnet, would the magnetic force be equal stronger or weaker if I used a battery with a capacity of 5000V and 0.5A (2500Watt) or 0.5V and 5000A?
Or will it be ...
2
votes
3answers
678 views
Why do we need brushed motors?
Looks like brushless motors are more convenient - no brushes means no maintenance required. For example, power tools manufacturers often cite that graphite brushes need to be replaced every 50 hours ...
4
votes
4answers
979 views
How does a guitar body affect electromagnetic pickups?
If the pickups are just electromagnets detecting vibrations in metal strings, what effect does the guitar (size, shape, type of wood, solid body, hollow body) have on the pickups?
Most argue that the ...
2
votes
1answer
237 views
Should I avoid placing a SMPS inductor close to a magnetometer?
I am designing a board, which has a high current (~2A) buck-topology switch mode power supply on it, which uses an unshielded SDR0805 inductor. About 4cm from it, there is a magnetometer (combined ...
2
votes
1answer
436 views
Safely connecting an solenoid/electromagnet to a switch-mode supply
I'm currently working on a project that involves hooking up an arduino, a cellular shield, and an electromagnet (in this case, one of those old fashioned ringer boxes with a bell powered by ...
4
votes
2answers
439 views
How to build a constant magnetic field source for a “railgun”?
I'm trying to build a device similar to railgun. It will have two rails and a conductive movable bar in-between. At one side, I'll provide voltage source and a resistor. If I put it in a strong enough ...
10
votes
1answer
1k views
How does a Theremin “antenna” work?
I always assumed that the shape of the antennas was important; a vertical monopole for pitch and a horizontal loop for volume, thinking that this minimized their interference with each other. But it ...
