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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Antenna pi-network matching High or low pass?
I am a beginner in RF system design and I have some questions.
I have a PCB trace antenna, I need to tune it to 2.45GHz, this is for Bluetooth low energy communication.
I want to use a pi-network for ...
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2
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What should be the core size, SWG #, # of turns for 100VA isolation transformer to run 100 watts bulb at .5 amps & 230 volts?
I am a certified computer programmer, but not an electrician. After researching on google, youtube, reading few books and referring to some local technicians, I made a transformer on a toroidal core ...
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Does the needle of the galvanometer point in the direction the current is flowing?
Probably a little too simple for this site but I read different answers to this so I thought I would have the electricians weight in on this.
If this is true what law of electricity is it using to do ...
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Can a weak external magnetic field damage a magnetron?
I have a 40-year old microwave oven. I temporarily attached a magnetic flashlight to the side of it. Its 5/8"-diameter magnet is likely a neodymium magnet, strong enough to secure the 10-ounce ...
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What role do electrons play in a circuit other than establishing an electric field?
In a simple electric circuit consisting of a load (such as a filament lamp) and a power source (a 5 V battery), when the switch is turned on the electrons experience a "displacement" which ...
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Transmission Line model [closed]
Can some one explain me why exactly classical circuit theory fails to account for the wave nature of EM fields and how the transmission line model accounts for it better
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2
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Inductor and transformer with open magnetic core
I have some troubles to understand the principle of:
1-> open core inductor
2-> open core transformer
Let us talk about open core inductor as the one above:
If we think about it as an ...
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3
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369
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Why is RTD immune to electro-magnetic fields? [closed]
Thermocouples may have added voltage & induction heating induced in a magnetic field, throwing off the measurements.
A Resistance Temperature Detector (RTD) is said to be a good alternative. Why ...
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Is there induced current if a horizontal rod move sideways in a vertically uniform magnetic field?
In figure 1, there is a metal rod connected with a wire in a uniform magnetic field. If it is moved sideways and a part of its body is leaving the field, what will happen?
Is there induced e.m.f.?
Is ...
2
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2
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Why is my maths saying that increasing turn count will decrease magnetic field strength in an AC coil?
I’m trying to make a device that can propel rings of conductive material upwards and make them hover, like the one seen in this video at 6:24, albeit on a smaller scale. I got a stepdown transformer ...
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Why are patch antennas used instead of planar dipole antennas?
As far as I know, the major advantage of patch antenna over dipole antenna is its directivity. If the planar dipole antenna can achieve the same directivity then why do we use patch antennas? Are ...
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Importance of power factor [closed]
I understand the difference between reactive power, but why is power factor so important? A system with low PF draws more current; well wouldn't a larger load, be it resistive or reactive, draw a ...
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A question on radar cross section of rain by using radar reflectivity factor
The question is one of the past exam papers of the RADAR 1 course given in TUDelft, unfortunately, solutions are not provided to the past paper yet.
The question:
What will be the radar cross-section ...
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2
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Why are microwaves unidirectional and radio waves omnidirectional?
I understand that any wave can be given direction using a setup like a phased array.
As I read about the properties of EM waves, I find that microwaves are unidirectional in nature.
What is it about ...
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RFI noise impact on ADC
I am trying to debug the issue where RFI noise is increasing the ADC's analog input values when a Walkie-Talkie is switched on (transmitter mode, 470MHz) nearby.
What could be the quick tips to ...
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2
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Does the direction of coil winding impact the direction of induced voltage?
I have taken and modified a bit the following image from a similar question, where it was explained that the direction of the coil winding does not impact the direction of the current: Does coil ...
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Armature Winding
This might seem like a silly question, buy why aren't armature windings usually done in a simple manner as shown in the image, why does it have to be more complicated such as lap winding etc?
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How does a gold leaf electroscope measure voltage?
It’s my understanding this device can be used to measure voltage. How is this accomplished? What electromagnetic equations are applied and how is it calibrated?
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3
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Voltaic pile: question on components
I have some questions on voltaic pile components.
The following show images of the voltaic pile. The vertical pile in I1 has four outside (labeled m in Fig 2) bars and one bar in the center ...
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5
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How does a voltmeter determine voltage?
For example, using a battery. Does the meter place a small resistance in line with the two terminals, then measure current and solve for V using V=IR?
I’m looking for the general theory.
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3
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Inductance depends on the number of turns in a solenoid. Is this the case with reluctance as well?
The total flux (\$\Phi\$) through an solenoidal inductor of length \$l\$ and \$N\$ turns is proportional to the current through the inductor and the inductance \$L\$ of the inductor according to
$$\...
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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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Tesla AC motor: question on component
The following is a picture of Tesla’s AC motor patent. Does anyone know what appears to be slip rings on the left end of shaft a’ coming from generator G are for? Also, what is the function of the ...
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1
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Tesla AC motor: what is this component?
Can anyone explain how the pictured component that looks like a long stem connecting to the generator G operates? Most specifically of the left side connecting to the terminals?
My understanding is ...
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Tesla’s AC motor: questions on operation
The Tesla Patent for the AC motor claims a circular disk can be used in place of the rectangular piece of steel which rotates in the motor. The disc is more efficient. I can see how the rectangular ...
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How can one calculate at surface the electric or magnetic field strength for 50Hz 240VAC wire at 1 meter depth?
How can one approximately calculate at surface the electric or magnetic field strength for 50Hz 240VAC wire buried at 1 meter soil depth for a given current?
Say in sandy clay soil with no mineral ...
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Lavet type stepper motors design guidelines
For a client we need to provide a Lavet-type stepper motor - I'm looking for some design guidelines - there seems to be very little technical literature on this type of motor.
Wikipedia seems to be it
...
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1
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GMR Sensor voltage output into magnetic field
I used a GMR sensor (Model AA003-02) inside a electricly adjustable homogenous magnetic field generated by a long coil. In other words the current is proportional to the magnetic field strength. ...
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1
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Modelling a single trace PCB?
I am trying to model a PCB trace as a R, L, C circuit.
Assumption: My PCB has a a single trace running through it. Just giving input from one side and taking output from other. There is not even a GND ...
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2
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Why is the bridge rectifier circuit widely used to make power supplies?
Why is the bridge rectifier circuit widely used to make power supplies? Which is better - a bridge rectifier with capacitor or without capacitor?
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1
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Frequency response of antennas
Electromagnetics and antennas are not my main area of expertise. However, I have a specific question about antennas that I want to get right in order to make sure my signal processing is right.
What ...
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2
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How to determine the radiation pattern of a receiver antenna
I am designing a receiver antenna for a wireless power transfer application.
The transmitter is a 2m x 2m horn antenna array that transmits a power signal at a frequency of 35 GHz from 100 meters away ...
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1
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How does balancing currents within a cable or conduit cancel its magnetic fields?
I know the NEC requires all current carrying conductors of the same circuit to be included in the same cable or conduit [300.3(B)], but why? I think it is because the magnetic field generated by ...
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2
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DC Vacuum Contactor Coil - Failed Close
I am using a 350A DC, normally open vacuum contactor that experiences a failure while the contactor is closed (coil energized by 24VDC) for an industrial 1000VDC application. The manifests as the ...
2
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2
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Real life example of lossy medium
I’m learning about electromagnetic fields in class and a real life example of lossy medium would be helpful.
I also don’t know how intrinsic impedance connect connects to lossy medium - probably ...
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Wierd noise on GND when I touch a metallic object to it
I am facing a problem.
I have a PCB designed which fails ESD tests.
The PCB is powered by an external power supply that provides 12V to the system (from 240V AC.) The power supply is CE certified and ...
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0
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When the electric field EMF radiation hits tin foil why does it result in a magnetic field?
I have a cheap Erickhill EMF reader that measures “electric field” and “magnetic field”.
I’ve been experiencing an odd phenomena that I can’t quite explain of a electrical sound emanating from a ...
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Planar PCB inductor coil simulation
I am working on a planar PCB coil with a complicated shape (not the traditional circular/rectangular spirals.) It is essentially an inductor made out of PCB traces. I want to figure out the inductance ...
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1
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Difficulties in tuning magnetic levitation system on Arduino and MATLAB?
So I am dealing with a project that revolves around magnetically levitating an object below an electromagnet. I created a transfer function of it after making a mathematical model of it, and got this ...
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1
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What are "dummy terminals"
This picture is in datasheet of one relay:
From this picture I assume that if there's current flow between 1 and 8 pins, the relay will connect 3 and 4, right? What are "dummy terminals"? ...
3
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2
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Does coil winding impact current direction? (Lenz Law)
When a magnet is moving toward a wire loop north-side first, the current goes counterclockwise according to the magnet's perspective, as shown in the image below from Wikipedia. Now, consider a ...
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0
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Strange result in modelling magnetic levitation system?? Negative Transfer function?
I'm working on this magnetic levitation system project where I basically levitate an object under an electromagnet using an Arduino. Currently, I'm stuck at the graphical simulation of my transfer ...
2
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1
answer
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Difficulties in modelling magnetic levitation system?
I am currently working on and writing a project (not homework) surrounding magnetic levitation with an electromagnet having to levitate an object underneath itself. I have taken a look at relevant ...
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1
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How can I read an RFID tag at the back of a phone FROM THE FRONT?
I'm discovering RFID applications and I would like to be able to read an RFID card I strapped to the back of my phone (the most convenient location for me) by just putting the phone face down on the ...
4
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1
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How does electromagnetic shielding work?
How does electromagnetic shielding work in cables? I learned from school that foils are used as shields in coaxial cables to "shield" them from external electric and magnetic fields. It also ...
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1
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How do I mathematically model a magnetic levitation system?
I am working on a magnetic levitation system project using PID control, and I am getting confused as to how I am supposed to mathematically model this system for my paper. Where am I supposed to start?...
2
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2
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Does acceleration come from a change in current?
I have a current connected to a wire and let's say when we measure the current at a particular time it reads differently than it does after some time.
Does this imply the current is AC?
I'm asking ...
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How do I build an electromagnet?
I want to make an electromagnet that can lift a paper clip off of the ground from a short distance (probably 7 to 8 inches). I naively thought of making an electromagnet as a simple task (because of ...
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1
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Computation of DC motor parameters [closed]
How does one compute DC motor parameters instead of measure? Example: inductance, backemf,torque?
Would one use a EM simulator or is there another way?
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1
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How do clamp multimeter sense presences of AC voltage?
If a clamp meter is taken near a AC supply line, it's AC voltage sense LED starts to glow. The same coil that is used for current measurement is used to sense the presence of voltage. As far as I know ...