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 the site.

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Question about RF waves and it's effect on electronic devices

Could a let's say 50 W RF wave (2.40 GHz and 5 GHz) cause disturbance in nearby devices like Laptops? (Data corruption, random opening of applications and programs, random commands, etc.)
AndyCrypto's user avatar
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1 answer
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Electromagnet doesn’t have power [closed]

I have so problem with an electro magnet, I mean it seems a little weak to me. What could I do to improve it’s power? Battery: 3.7V 8800mAh Also, I had the wires in small parts so that’s the reason ...
Gabriel Stan's user avatar
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Energy regenerative snubber for flyback converter

I am trying out the regenerative snubber design in https://core.ac.uk/download/pdf/215381319.pdf page 13. The circuit configuration is shown in the figure below: I am unable to derive the following ...
p_karis's user avatar
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2 answers
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The idea of voltage in the ideal inductor equation

In a book that I have been reading (Practical Electronics for Inventors 4th ed by Paul Scherz and Simon Monk), I came across the equation on pg 129 for for inductor $$V_L = L \frac{di}{dt}$$ where $$...
Iberico's user avatar
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1 answer
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Converting air compressor to gas but leaving ac motor on

I have a compressor with the crankshaft being the the front part of the shaft of an A/C motor's armature.. The rear of the AC motor's armature has enough protruding shaft to put a pulley on it and ...
De ho's user avatar
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1 answer
103 views

Why is resistance (inversely) proportional to area instead of circumference?

TL;DR From the Veritasium-vs-ElectroBOOM debate about the 1 m / c question, it seems to me that most properties about conductors depend only on surface charges. So shouldn't quantities like resistance ...
eccentricOrange's user avatar
2 votes
2 answers
61 views

How can a transistor behave as a switch in the saturated region

how can a transistor behave as a switch in the saturated region when it is in forward bias mode in the saturation region and the collector current may become zero, when a transistor is used as a ...
sachin's user avatar
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2 votes
2 answers
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Does operating an iron core near its saturation field reduce performance?

I am sizing an iron core for an electromagnet, and I am uncertain if there are disadvantages to operating close to the saturation flux density. If the saturation field is X, would it be better (more ...
Arad's user avatar
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2 answers
87 views

Reflection coefficient of a transmission line with discontinuity

I have a question, let's say that we want to calculate the Reflection Coefficient that we see by watching from left to right of the red-line this circuit: Let's say that: Za= Equivalent Impedence of ...
Martino Pistis's user avatar
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1 answer
107 views

Propagation speed and capacitors charging speed of transmission line

I am a bit confused on the speed of voltage propagation in the transmission line and I hope someone can enlighten me. I understand the speed of step up voltage propagation is in the same order as the ...
eyew18's user avatar
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Problem understanding lossless T-Junction divider

I am studying how the lossless T-Junction divider works. I am going to assume that the susceptance in the junction is 0 for simplicity, and it is not relevant to my question. The structure of a T-...
fraghotmailcom's user avatar
1 vote
1 answer
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FEMM simulation not returning expected force from electromagnet

I have an array of 8 air-cored electromagnets. Each one activates sequentially(with previous ones staying activated) to pull the N42 Neodymium magnet array to the end of the array, with the force ...
Yassin's user avatar
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0 answers
72 views

HV and LV transformer coupling not working, no current from LV transformer?

I am trying to couple a high voltage transformer (automobile coil) 220 V to 10 kV, with a low voltage home made transformer 220 V to 6, 12 V (think MOT but bigger). I have tested/used the LV ...
user1570144's user avatar
1 vote
0 answers
31 views

Are transistors on MMICs considered lumped elements?

Are transistors, in practice, always small enough to be considered lumped elements in Monolithic Microwave Integrated Circuits (MMICs)? Similarly for discrete transistors used in hybrid microwave ...
jramsay42's user avatar
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How do I find the torque of a simple electrical motor?

I created a simple electric motor following Khan Academy's tutorial, and now I am trying to figure out how I can find the torque from it (which should be quite small). Here is an image of the setup ...
WChan's user avatar
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2 answers
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Is Lorentz-Force the same as electromagnetic force?

I have been doing some research on the Lorentz force law because I am currently learning about AC and DC electric motors. I have been stumbling onto the phrase "electromagnetic force" and &...
WChan's user avatar
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Visualizing current flow in transmission line

This may be a trivial question, but I am not sure how current flows in certain types of transmission lines. Consider for example a coaxial cable working in its TEM mode. The wave travels perpendicular ...
fraghotmailcom's user avatar
1 vote
2 answers
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Coil winding direction in a shaded-pole motor (4-pole)

I have rewound a shaded-pole motor (4-pole). It's wound around the stator in a clockwise motion and around each coil in a counter clockwise motion. Is the winding being incorrect the reason why the ...
Thorin drake's user avatar
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Want someone to review my Helmholtz coil design to see if I am missing something obvious before I fabricate it?

I am planning to construct a Helmholtz coil and wanted electrical engineers to take a look just so I know I am not overlooking anything. The max field strength I am looking for is 200 Gauss. I ran ...
assasinchop7's user avatar
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Calculate inductance of a coil with an iron core inside

I want to calculate inductance of a coil with an iron core inside. The iron core is not vertically centered, but it is still aligned along the axis of the coil. I know that FEMM softwares and ...
MohammadAli Zeraatkar's user avatar
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1 answer
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Is the current that is on the surface of the area surrounding a current carrying wire in Ampere's Law the same as what flows in the wire?

I am OK with the first 3 of Maxwell's equations but on the 4th equation I need to first figure out Ampere's law. What is confusing me is the surface of the area that is surrounding the current ...
Sedumjoy's user avatar
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How does this motor work?

I have been on a bit of a quest to find some sort of linear motion device to compress a spring with 15kg of force 80mm at 1600mm/s, with continuous duty cycle, ideally under $40. So I was digging for ...
Yassin's user avatar
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0 votes
3 answers
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Linear Motor Design

I previously uploaded a question on trying to make a solenoid attract a magnet 80mm away, however this ended up being an impossible ask due to solenoid's having a max effective attraction distance of ...
Yassin's user avatar
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1 answer
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Strong Compact Solenoid Design

I have a spring that I need to compress 80mm. To do so requires approximately 15kg of force. To compress the spring, I will have the spring in front of a piston head. The piston head will have a ...
Yassin's user avatar
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2 votes
0 answers
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How can a wire be influenced by a electromagnetic field?

I have a problem in one of my project. Here are some details: A train is moving on tracks. To know its location, some beacons (transmitters) were placed at different locations in between the two ...
MaxenceV's user avatar
4 votes
1 answer
68 views

What role does permanent magnet strength play in BLDC/PMSM performance?

It seems to me like stronger permanent magnets are preferred by motor designers, but my current understanding of what role they play in performance is fuzzy at best. I would assume that stronger ...
TheDarkSaint's user avatar
2 votes
1 answer
53 views

What types of inductor cores exhibit magnetization?

My understanding of magnetization in core memories is as follows: a bit is written to an inductor's core by magnetizing it, by applying a large current. Later, the bit is read by observing the effect ...
personal_cloud's user avatar
3 votes
1 answer
167 views

Predicting EMI/EMC Issues from Microcontroller AC Spec Rise time fall time

In one of his video Rick Hartley says signals with fast rise time can cause EMI/EMC issues. I am using FS32K148UJT0VLQT in my design. In my board this controller is working at 5 V supply. Below image ...
Hari's user avatar
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1 vote
1 answer
70 views

Park transform, why do we use the electric angle and not the mechanical angle?

In the control of a motor with a multi pole-pair permanent magnet rotor the Park transform is done (if I am correct) using the electrical angle, and not the mechanical angle. If we use the motor as a ...
Fabio Dalla Libera's user avatar
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1 answer
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Selection of the utilization factor for the calculation of the transformer for the DAB converter

DAB Converter: When calculating the parameters of a transformer, it is necessary to know the utilization factor of the transformer (Ku). Here it is 0.3. The utilization factor of the transformer ...
Delta's user avatar
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0 answers
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ADXL345BCCZ output problems in a high voltage, high magnetism environment

I'm trying to find a fault in an ADXL345 being used in a very specific application where it is near both high voltage and high magnetism. Is it known to suffer in this application? The circuit was ...
Fishman's user avatar
0 votes
1 answer
85 views

How does current flow in a circuit with a capacitor, Can you please explain the concept of displacement current

When a capacitor is coupled to a DC source, current begins to flow in a circuit that charges the capacitor until the voltage between the plates reaches the voltage of the battery. How is it possible ...
Hari's user avatar
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1 vote
0 answers
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How could you make a polarity-switched electromagnet at home?

For context, I have lots of electrical parts and I am looking into ways to make a small polarity-switched electromagnet out of the parts I have. I can Information on the parts I have if needed. If ...
3xion_Stack's user avatar
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0 answers
45 views

Relation of KV to speed in BLDC motors

The KV parameter determines the angular velocity of a motor for some voltage. I can't wrap my head around how the same supply voltage can result in different angular velocities if (I'm also unsure ...
3am_enlightment's user avatar
0 votes
1 answer
108 views

How close to electronics can a relay be?

For example this relay - how close can it be to microcontroller, like PIC? What if I have few relays - can I put them next to each other? What if they carry high AC (~40A) current - would that also ...
Ri Di's user avatar
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0 votes
1 answer
48 views

Reed Switch alternative IC, AMR or TMR

I have a prototype that I have built which has 4 positional reed switches arranged in a square around a circle. There is a rotating magnet as shown below: I would like to replace them with solid ...
Jaspal Singh Rathour's user avatar
1 vote
4 answers
343 views

Zero voltage on voltmeter means zero resistance and infinite resistance?

I am pretty sure this is a very easy question but I am having brain lag, on a digital/analog voltmeter, what is the difference between zero volts (or very close to zero i.e. 10 mV, -4 mV ) when the ...
Shams M.Monem's user avatar
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0 answers
51 views

Can anyone explain electrical and mechanical angle of BLDC motor?

If a 3 phase 6 pole BLDC motor is 120 degree trapezoidal/block commutated and 6 switching sequense is required. How do you calculate the electrical degree per pole and mechanical degree? How many ...
Nh K's user avatar
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1 vote
0 answers
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How to simulate a Large Structure at low frequency in CST Microwave Studio?

In CST Microwave Studio, I attempted to simulate a large (215x30cm) loop structure at 1kHz. However, CST gives a warning of 'too large' mesh size. The mesh size increases up to 6 Billion, however, if ...
Pessentrau Optiarou's user avatar
3 votes
1 answer
88 views

How does the floating light bulb rotate and power off? [closed]

I am trying to understand on a high level, how famous floating light bulb actually works. https://www.floately.com/products/volta-light-bulb I kind of understand how it floats and how it is supplies ...
ng.newbie's user avatar
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3 votes
1 answer
94 views

Is it possible to design an antenna with constant antenna aperture (that doesn't vary with frequency)?

As per the title, I'm interested to know if it's possible, either theoretically or practically, to have an antenna design which has a constant effective aperture (antenna aperture - these are the same ...
Christian's user avatar
0 votes
0 answers
59 views

How do I calculate the number of turns needed for a coil gun?

I've got 20m of 1mm in diameter copper enamel wire that I coiled around a PVC pipe as neatly as I could. I powered it with around 20V and put a small iron nail near the pipe but nothing happened. How ...
Joshua's user avatar
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1 vote
0 answers
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Transformer Design and Ripple Formula

When I was researching flyback inductor I saw a formula which is showing the effective transformer core volume with related the ripple factor. r = 2Iac/Idc = ΔI/Idc Where does this formula come from?
John Reese's user avatar
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0 answers
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Derivation of self-inductance of a long wire: Is my interpretation correct?

https://physics.stackexchange.com/questions/11799/derivation-of-self-inductance-of-a-long-wire https://physics.stackexchange.com/questions/176783/flux-linkage-inside-of-a-conductor https://physics....
İbrahim İpek's user avatar
1 vote
1 answer
67 views

Characteristic impedance: TDR (function of position) versus VNA (function of frequency)

A TDR gives you the characteristic impedance of a transmission line as a function of position. You can also measure the characteristic impedance of a uniform transmission line using a VNA, which gives ...
qtc0's user avatar
  • 107
4 votes
1 answer
201 views

How does energy travel in the system in a conducted RF immunity test,?

I have a question regarding some conducted RF immunity (IEC 61000-4-6) tests. We inject noise starting at 150kHz until 80MHz. The signal injected is AM at 80%. The level is 20Vrms. Here is the setup ...
Dimitar Zhekov's user avatar
0 votes
1 answer
90 views

What is the utility of inductors in circuits? [closed]

I was wondering what all the possible purposes of inductors in electrical circuits are. Inductors, as I understand, are wires wrapped in a helical pattern around some sort of solid material or simply ...
Runsva's user avatar
  • 159
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0 answers
42 views

How can I calculate the coupling coefficient between two coils?

I have two planar, circular coils of different number of turns, inductances, and radius, stacked on top of each other. How can I calculate their coupling coefficient (k) based on their properties and ...
Theodor's user avatar
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-1 votes
1 answer
42 views

Charges in receiving antenna and polarization if alternating current is changed to stay high

A dipole antenna receiver placed in parallel to a dipole antenna transmitter will have a current induced in the opposite direction to the current in the transmitter. This causes charges (electrons and ...
BipedalJoe's user avatar
4 votes
3 answers
1k views

Why is it not standard practice to integrate the output of an antenna?

This is a follow up question from my question answered here: Why does a loop antenna not measure the differential magnetic field? Essentially I just found out today that we are actually measuring the ...
Christian's user avatar

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