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.)
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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 ...
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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 ...
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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 $$...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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-...
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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 ...
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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 ...
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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 ...
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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 ...
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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 &...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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?
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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....
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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