Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [emf]

137 questions
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Why does analysis indicate that ground lifts do not fix ground loops?

Note: "Ground loop" in this question refers to a ground loop caused by linked magnetic fields. (Sometimes ground loop refers to slightly different scenarios.) Recently I've been looking into ground loops a lot since I've encountered them in circuits…
PersonWithName
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Thermal EMF (seebeck effect) on PCBs

Can poor PCB fabrication process / assembly, and the type of solder used cause thermal EMF (seebeck on PCB) problem? Is it affected by the type of the material used? For example, quality of plating, vias, use of different metals such as gold, tin,…
MAA
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How should I understand back-EMF in an inductor?

I have a circuit made of a MOSFET that pulls the lower side of an inductor to ground while the other side is connected to a DC voltage source as follows: Then it is very simple to describe what's going to happen when the gate goes high. According…
menr1232
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What are the consequences of connecting two motors in parallel?

I am using two DC motors rated at 36V and maximum current draw of 5A. To reduce the number of motor-controllers, I am planning to connect them in parallel. The two motors are required to run at the same speed, so wiring them in parallel will ensure…
Jaghvi Mehta
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"Where" does back EMF appear in motor?

I've been trying to understand EMF, specifically back EMF in electrical motors, such as for example a setup like this: Say that we apply a voltage to the brushes. I understand that once the rotation gets going, a current will be induced by the…
Daniel Nilsson
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How do DC motors work with respect to current, and what consequence is the current through them?

Motors in general have always been a difficult subject that I cannot fully wrap my head around. Considering DC motors, what determines the rate at which the motor spins? It was my understanding that a permanent magnet created the field by which the…
sherrellbc
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Measuring back EMF induced current with multimeter

I have built a solenoid with copper. It is 19 cm long, it has 64 turns and the radius is 1.5 cm. To trigger back EMF, I use a permanent magnet that has the same surface as the cross sectional area of the solenoid. I put the magnet on one end of the…
Rabih Sarieddine
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Sparks on grounded metal bodies on lighting strikes in the nearby (two miles)

I have a strange phenomenon in our mountain cabin, on the Italian alps: lightning strike on the nearby (not so near: < 2 miles) causes audible / visible sparks on: electric / fire wood water heater pipes (very frequently) LED spotlights…
SpecialFx
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Ideal Op Amp and its Input Voltage

In an ideal operational amplifier, I understand that the inputs draw no current (due to infinite impedance). So, in the example below, the value of Vp would equal the value of the EMF (because there is no voltage drop across the resistance), which…
Sean M
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What properties of metal makes make them suitable as EMF shielding material?

What properties of metals make them effective at shielding against EMF, and which metals are typically used? How does Aluminium, Steel, Copper and Lead compare?
Mr. Developerdude
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Harvesting Back EMF Possible?

Let me start by saying that I am not talking about the free energy or "overunity" idea of back EMF. When searching around for information I can only seem to find information from free energy sites, which isn't too helpful (perpetual motion and all…
Jarrod Christman
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Detect multiple corn bags through wood with a sensor

I'm working on a project for school, and wondering what options I have for detecting the corn bags through a piece of wood. More specifically, we are creating an automated cornhole scorer. Sources of images are those: wood and scorer. We have…
user39948
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How can I clamp the voltage precisely from the back EMF of a brushed DC motor?

I am using DRV8412DDWR in a medical product, where we are driving two DC motors (graphite brushed) bidirectional using PWM. In our application, we have to suddenly stop the motor. When we do that, we are seeing a back EMF current of ~1 ampere due…
Nice Guy
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Charging a capacitor with a ferromagnetic generator

I am doing my internship and the company is making a ferromagnetic generator which indeed uses magnetic transition to create a flux and finally EMF. I am assigned to design a circuit which takes the EMF created and store it in a capacitor. I have…
Ekin Alparslan
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Is there an actual need for the concepts "emf" and "back emf"?

Given a two-terminal element where you can only measure the voltage across terminals \$v(t)\$ [\$v_{ab}(t)\$] and the current \$i(t)\$ defined as entering the positive [a] terminal, there doesn't seem to be a need to introduce concepts as "emf" or…
Petrus
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