Questions tagged [electromagnetic]
Electromagnetism, or the electromagnetic force is one of the four fundamental interactions in nature. This force is described by electromagnetic fields, and has innumerable physical instances including the interaction of electrically charged particles and the interaction of uncharged magnetic force fields with electrical conductors.
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I am wondering if magnets can be safely used to connect power from one to the other? [closed]
I am thinking of trying to create a extension cord that can be taken apart or separated as needed. And rejoined at any length of cord but connected only through magnetic connections. So I'm wondering ...
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Toroidal/cylinder single turn transformer to circular waveguide coupling
The questions is mostly in the title. Is it possible to effectively couple a toroidal/cylinder shaped ferrite core with thick spread out single turn of wire to a circular waveguide?
The idea is that ...
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Scattering matrix of quarter-wave transformer
I am trying to solve for the scattering parameters of a quarter wave transformer. The example that I am given is a transformer with characteristic impedance 100 Ohms, and the reference impedance (...
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Multimeter range
I've been using a small multimeter meter and the problem is that anytime I want to measure amperage that exceeds 200 mA, I have to switch the red probe the 10 A port. Unfortunately, I can't get the ...
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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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Time-Varying Inductance in Electrical Systems
How to derive and solve equations for electrical systems when the inductance of an inductor is not constant and changes over time?
I'm familiar with the standard equations like E = 1/2Li^2 or V = Ldi/...
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Design of an antenna on a PCB card emitting between 1000 and 5000 Hz
I would like to create an antena on my PCB thanks to copper track. My antenna has to be a square like a coiled coil in order to emitt a magnetic field.
Is it possible to create an antenna like that ...
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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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When an electromagnetic relay is switched on, it shows a dip in the coil current for a millisecond but then increases again. why?
I am currently studying the effects of current on the coil of an electromagnetic relay and came across this graph:
Image source: Ramirez-Laboreo, E., Sagues, C., & Llorente, S. (2015). A new ...
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Spending money on gold cables [closed]
Recently a friend of mine spent several tens of euros to buy a set of gold connectors to connect to the audio amplifier, justifying this expense on the grounds that they were gold and therefore the ...
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Faraday’s Law and voltage balance
Does anyone know how to use Faraday’s Law and voltage balance to explain this equation?
I don't understand where jw comes from.
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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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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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Why does a loop antenna not measure the differential magnetic field?
I am making the assumption that a loop antenna is essentially an inductive loop and behaves as such, please let me know if this is incorrect.
Knowing that the voltage (emf) across an inductor is ...
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Transformer Phasor Diagram And Circuit Diagram
I have been reading the construction of a practical transformer and facing difficulty in understanding the phasor diagram of it.
When we connect \$V_1\$ supply to the primary side, say \$V_1 = sin(wt)\...
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Finding resistance between two conductors
For my electromagnetic-field class we are asked to calculate resistance between two electrodes shown as below.
The part c(i) is just a simple resistance question using the formula R=pl/a.
I don't ...
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Understanding voltage in simple electromagnet and DC motors
I made a simple electromagnet with enameled copper wire wrapped many times around a metal allen wrench. I attached the electromagnet to my PSU and it works great, but I do not understand the voltage ...
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What does this coil do in car door handle
This door handle is from a Range Rover L405. I tried searching car manufacturer's documentation and car door handle tear downs, but I cannot find what this coil is doing in the the door handle.
This ...
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Single phase transformer circuit
A single-phase transformer with a rating of 50 kVA, 2300/230 V, 50 Hz, has the following resistances and reactances (the primary is the side with the lower voltage):
The transformer supplies a load ...
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Help with AC generator
Why is the multimeter not displaying anything, if I have a copper wire next to a rotating magnet. The magnet moves at 100 RPM and the whole enameled copper wire is coiled and has a total length of 2 ...
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Is EM wave always time-harmonic in free space?
Is EM wave always time-harmonic in free space ?
Can non-time-harmonic EM wave not exist?
user331400
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UHF RFID antenna
When designing a UHF RFID antenna, besides matching to the chip, is there some matching to air that needs to be done (for example, to the characteristic 377 Ω)?
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Applying an electrical field to a particle in Ansys HFSS
Does Ansys HFSS have the ability to show the applied electrical field to a particle?
I designed a coplanar wave guide in this software, something like in this video.
Is it possible to put a particle ...
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Is an EMP weapon a real threat to power grids?
I do not see how an EMP is realizable. The idea is a nuclear bomb detonated high enough will release a strong enough EMP to take out a country's power grid without damaging infrastructure. In my ...
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Winding coils in an AC generator
Assume a coil arrangement in an AC generator like the one seen below:
Given that the magnet has one pole on each side (2 poles in total in the magnet), how must the surrounding coils be wound? In ...
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Noise calculation using RX channel bandwidth
I am working on calculating the thermal noise expected for a long-distance telemetry system based on the RFD900+ radio. According to the documentation, this radio is based on a Silabs1030 ...
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In an electric machine, does the force act on the copper conductors or on the iron and why?
My question arises from the following reasoning:
Starting from the basic explanation that a force acts on a current-carrying conductor in a magnetic field, I realized that, more concretely in ...
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Can you explain the function of this circuit?
I am interested in implementing the motor in this video. I understand the whole process and the physics behind it, but I do not understand the function of the circuit in the same video as I have such ...
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In which direction is the microphone signal transported?
So I understand the general principle of how the audio signal is transported. I also understand that audio signals can be distinguish between AC and DC.
But let's say we have a TRRS Jack like below. I ...
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How can I make an RF source with various frequencies?
I have been working on a new electromagnetic shielding material. A part of the project is testing it and finding its electromagnetic shielding effectiveness (SE).
For instance, I could use a ...
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Ways to detect close proximity ( ~15cm) of several individual child objects to a mother object [closed]
I'm working on a design project for a university course exam where several small child objects have to detect whether they are in close proximity (~15cm) to a central mother object and switch their ...
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What is the sum force acting on a test charge due to a line charge?
I want to calculate the sum force acting on a test charge due to a line charge. Please see my way of solution below. Can somebody check if Equation 1.7 is correct or not?
Figure 1.1 a
Figure 1.1 b
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Why does my homopolar motor generate intense heat?
I assembled a homopolar motor based on YouTube videos. I got it to work like you see in the videos, but also slightly burned my fingers in the process. After "turning off" the motor (i.e. ...
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Antenna polarization and loss factor
I am trying to solve the following problem:
I know that in the +z direction:
linear polarization requires the field vector to have:
one component OR
two orthogonal linear components that are in ...
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How to find the points between which EMF is induced in a loop with resistors?
I recently came across a problem on Faraday's law, which had multiple resistors. The circuit looked something like this, with the loop rotating clockwise.
Personally, I felt that there would be three ...
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Across which terminals is EMF induced in this circuit?
If I were to place a circuit such as this in a changing magnetic field, across which terminals would an EMF be induced? If the field were into the plane
My intuition suggests across all wires lying ...
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Magnetic field strength of wire (Biot-Savart Law)
Hello :), as you can see in the third picture, I drew a circle on the glass plate in the second picture and measured the magnetic field strength at the black point in the third picture when passing ...
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Where does the Step-Down Convertor used as compare to RECOM DC/DC converter?
I am reading Step-Down converter and given the circuit below, which is a step down converter. It consists of a MOSFET, inductor, diode, capacitor
And if I compare it with RECOM component DC/DC ...
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Magnetic charging
I have a question about magnetically charging devices and would like to see if anyone can help.
I understand we have things like cell phone chargers that wirelessly charge using inductive technology, ...
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What is the difference between BLDC motors and servo motors? [closed]
BLDC motors and servo motors seem physically the same. I know servo motors can do torque control, speed control, and precise position control, but BLDC motors can only do speed control.
Are there any ...
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Should I use a magneto resistor and a solenoid to dynamically change resistance?
I am trying to make a resistor that can change resistance with a current value.
I was recommended to research electroresistance, so I did. What I concluded from it was that I should use extraordinary ...
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Significance of electric field for electromagnetic compatibility standards
All electromagnetic compatibility standards around the world for immunity to electromagnetic fields (radiated susceptibility test) mention the strength of electric field (V/m), but not the strength of ...
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Ground loop impedance when measuring pH of salty/conductive liquids
I have a reservoir of conductive liquid (~2000 μS). Inside that liquid are two sensors: a pH sensor and a conductivity cell.
The conductivity cell is a two-terminal device and submerged. When ...
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Designing AC kick solenoid lock
I am making a kick solenoid lock with AC.
I designed the circuit to run on 220 V, 50 Hz (household plug.)
The inductor (coil) is air core
500 turns, 150 meter (500 ft) in length with inductive ...
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Why do we subtract horizontal and vertical component of a electric field?
I was solving a question of electrostatic which is: Find the electric field at a distance z above one end of a straight line segment of length L that carries a uniform line large lambda.
My question ...
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Which topology should I use for energy harvesting
I am making a energy harvester design but am confused which of the following circuit should I use to amplify and filter my harvested voltage. The first topology is the synchronous switch harvesting on ...
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Calculating the capacitance of solenoid
I am working on a project where I need to create a fairly strong magnetic field (15~30 mT) with a solenoid. I realized it is not so easy to create a strong electromagnet. The solenoid is 6.5 cm long, ~...
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Phase Shifted Full bridge converter transformer design
I am designing a transformer for a phase shifted full bridge converter for voltage up conversion.
My main concern is the efficiency, I am trying to reduce transformer loss to less than 5%. The total ...
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Unlatch a bi-directional latch when power is lost?
I need to design a feature for a system running on DC power that consists of a bi-directional actuated latch pin that instantaneously engages (extends) and disengages (retracts) via user command. A ...
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Tesla AC motor: operational question with field direction
I have a question on the direction of the magnetic field for each of the four windings of the pictured AC motor. I ask because the wires are not clearly labeled as to direction of each winding, in ...
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