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Questions tagged [emf]

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Are multiple EMF sources considered series-opposing in a parallel circuit? [closed]

In the parallel circuit attached, is it correct to call the loop A-B-I-J series-opposing? Or is B-I just another leg of a parallel circuit? Asked another way, does an opposing EMF source such as BAT1 ...
Bob Duncanson's user avatar
1 vote
1 answer
128 views

What are sources of extra low frequency magnetic field in a car with IC engine? [closed]

ELF analyser (16 Hz - 2 kHz) shows a magnetic field around 300- 2000 nT (at some position exceeding that) in car when petrol or diesel engine work. When RPM increase from idle to 2500 RPM, magnetic ...
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0 votes
2 answers
148 views

Example problem of induced emf in a 100 turn coil by a 100 turn coil which has 90kHz sin wave input voltage

Main Question: Let's say there are two coils each 100 turn and diameter 30 mm, And the second coil is perpendicular to the first coil's magnetic field (placed both coils next to each other; we can see ...
in.yssh's user avatar
  • 45
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0 answers
98 views

Example problem of induced emf in a coil rotating in the earth's magnetic field

I just recently learned magnetism-coil-faraday's law and I want to do some real world problem solving. Question: Let's say a copper wire coil (20 mm dimeter (r=10 mm)) of 3 turns (N=3) is on the ...
in.yssh's user avatar
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1 answer
64 views

Example problem of induced emf in a coil travelling with some velocity and perpendicular to the earth's magnetic field

I have a example problem which I created myself just out of curiosity, Question: Let's say a copper wire coil(20mm dimeter(r=10mm)) of 3 turns(N=3) is moving along the surface(Note-coil is not ...
in.yssh's user avatar
  • 45
0 votes
2 answers
92 views

EMF Meter: difference between AC magnetic, AC electric, and RF Measurements

let's consider this EMF Meter. Regarding its description, I have some doubts regarding what it is physically trying to measure: Detects all three types of EMF pollution: AC magnetic, AC electric, and ...
Kinka-Byo's user avatar
  • 3,550
2 votes
5 answers
1k views

How do transformers work?

I am a recent EE graduate and never really understood how transformers work. I am having trouble understanding how voltage is increased at the expense of current in a step up transformer. I understand ...
Darknight49's user avatar
-2 votes
1 answer
99 views

Offshore windfarm and real life effects on ocean fish [closed]

An offshore windfarm is being proposed which will consist of 170 wind turbines that will produce 1100MW of power. The offshore substations will utilize 15 miles of export cable. Part of their ...
Jax54's user avatar
  • 7
0 votes
1 answer
46 views

Increasing power of a standalone circuit board

I am a rookie at potentially upgrading some electronics and wanted to see if I could get a little direction on a potential first project. I purchased a small frequency generator and would like to ...
Scott Smith's user avatar
0 votes
0 answers
46 views

Why +ve charge(conventional current) flows out of the -ve terminal of a battery?

Please consider question 45 part c. In this question if I consider that the capacitor after being fully charged at 24V is now connected to a 12V battery, and since some heat will be lost as charge ...
Aditya Mukherjee's user avatar
1 vote
1 answer
101 views

Does AWG affect ethernet cable picking up EMF from electrical lines?

Currently, I have a client running an inappropriate cat 5E cable through a buried conduit, underground from their house to their pool control unit. This conduit also facilitates two lines of 120 V. ...
parsecpython's user avatar
0 votes
0 answers
56 views

Magnetic Field Produced By Electromagnet Perpendicular Winding

If I wound wire like a cylinder (blue) and then continued in a perpendicular direction like a toroid (yellow), what would the magnetic field look like?
br4n_d0n's user avatar
1 vote
3 answers
211 views

Shunt's thermal EMF (Seebeck effect) vs Kelvin connection?

While reading this Vishay document about shunts, I saw that temperature mismatch between the shunt's terminals can introduce a "parasitic" voltage drop which will in turn affects the current ...
HatimB's user avatar
  • 896
0 votes
2 answers
949 views

When is a zero-crossing SSR recommended for switching power to heating elements?

I am going to be switching power to three 2.7kW heating elements (240VAC, ~11.1A each) using a microcontroller. I'm trying to decide between mechanical relays and SSRs. The mechanical relays are much ...
user272901's user avatar
3 votes
3 answers
1k views

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 ...
Nice Guy's user avatar
2 votes
1 answer
208 views

How to find the terminal voltage of a series generator given output power and EMF?

A 12 kW, 120 V DC series generator has a series field resistance of 0.05 Ω. The generated EMF is 135 V when the generator delivers the rated load at its rated terminal voltage. The armature resistance ...
boseliker's user avatar
0 votes
0 answers
115 views

How do we calculate the cross section area and EMF in a solenoid?

Case 1: Consider an air core solenoid \$S_0\$ with inner diameter \$(d_{in0})\$ = 10 cm and the cross section area of the wire = 0.1 cm, outer dia \$(d_{out0})\$ = 10.1 cm. The number of turns in the ...
student0's user avatar
0 votes
1 answer
121 views

Coil for biggest EMF

I have a short (<1 s) pulse output that will be around 20 kV. Frequency is around 100-200 kHz. How would I make a coil that induces the biggest electromagnetic force (to radiate and mess with the ...
Jelle's user avatar
  • 77
2 votes
1 answer
83 views

Why do I have to connect ground to earth for my board to work?

I built a 3d printer myself, Im using an off the shelf controller board with a 24v 400w led power supply that I found for cheap on AliExpress. The quality of the power supply is far from perfect,It ...
Tiago Oliveira's user avatar
0 votes
2 answers
211 views

Understanding back EMF current in DC

I am trying to make a kicker solenoid. My circuit is: 12 V battery connected to DC step-up booster 300 V diode A10A. The diode is rated for 10 A and 1000 V. thyristor BTW69-1200 with external ...
Tito's user avatar
  • 465
0 votes
1 answer
150 views

Induced EMF polarity of inductor from bar magnet

I can't understand the polarity of an induced emf of an inductor from a bar magnet. I understand inductor voltage polarities in normal closed circuits in that an inductor produces a voltage drop when ...
Swiss Gnome's user avatar
1 vote
1 answer
85 views

Induced EMF in wireless LED

I have already asked this question here but this may be a better place. I have built the following circuit to power a wireless LED but my calculations and measurements do not give the same values. I ...
Dayton's user avatar
  • 113
-1 votes
1 answer
104 views

Inconsistent readings of magnetic fields between two electric vehicles

I measured the strength of magnetic field in two electric vehicles from different automakers. Both measurements were done while the vehicle was driving at non-trivial speed. Vehicle 1 showed under 0....
Alex-9710's user avatar
0 votes
1 answer
104 views

Fixing traverse on Guldmann GH2 (old title: Measuring EMF and terminal voltage with multiple batteries)

Suppose we have two 12V batteries as our source voltage. How can the EMF and terminal voltage be measured when using one 12V battery versus both batteries? Since terminal voltage deals with a closed ...
JustBeingHelpful's user avatar
1 vote
2 answers
1k views

Are those electric fields dangerous?

Is 8.6 amperes per meter, 70 microtesla, 0.70 gauss, 695 milligauss, safe on long time exposure? I am just worried.
Paul Delaunay's user avatar
1 vote
1 answer
205 views

Is an analog radio tuner more robust in a nuclear blast than a digital tuner?

Some radio receivers seem to have analog tuners (i.e. you turn a knob and it's completely mechanical), whereas others are more digital i.e. they can search for stations, save them as "presets&...
MHansen's user avatar
  • 11
1 vote
1 answer
198 views

Will primary flux & secondary flux (back MMF) in a transformer attract or repel each other?

I couldn't find it on google or may be I am not using the right keywords, if my terminologies are not sounding accurate, please bear with me, I am beginner in electrical engineering. When the primary ...
Yogie's user avatar
  • 129
0 votes
1 answer
188 views

How can I find the damaged phase in an RC drone's brushless DC ESC?

I have a damaged RC drone/quad. It has an all in one FC/ESC. The "all in one" is brand new. One of its motors is twitchy/does not spin. That motor is tested to be good. I tested it by ...
Jeffrey Edward Messikian's user avatar
1 vote
1 answer
69 views

Thermoelectric EMF problem for low voltage measurement load cell

The resolution of a load cell is highly dependent on its capacity. That's because the higher the resolution and the higher the capacity, the smaller the voltage change. For example, many companies ...
Herza Ryo's user avatar
-1 votes
1 answer
205 views

How does a CAT 4 radio detector work in passive mode?

According to https://www.radiodetection.com/sites/default/files/Theory-Buried-pipe-manual-V10.pdf in passive mode a CAT 4 radio detector 'looks' for harmonics produced on the 50/60Hz mains buried ...
user avatar
0 votes
1 answer
108 views

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 ...
user avatar
1 vote
2 answers
118 views

Could the electromagnetic field (EMF) from a power station disrupt wireless signals?

I know that power stations can generate an electromagnetic field, but is that field strong enough to disrupt nearby wireless signals, such as Wi-Fi, Bluetooth, cell service, etc? I'm sure that, in ...
Quentamia's user avatar
  • 113
1 vote
2 answers
841 views

Magnetic field shielding for electronics?

I am looking at an issue where a PCB design that is powered by a couple of CR2032 batteries will shut off all of a sudden in the presence of strong magnetic fields (around 15-40mT). However, when the ...
user1397215's user avatar
0 votes
0 answers
187 views

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 ...
A A's user avatar
  • 9
1 vote
1 answer
379 views

Back-EMF Concepts (Confusion)

I am trying to understand the current and EMF relationships in a brushless motor. Can someone tell me if this explanation is correct? Specifically, I'm interested in what is happening as the rotor ...
mrbean's user avatar
  • 802
0 votes
2 answers
220 views

Why the LED stays on all the time in this very simple circuit?

I build the schematics from https://hackaday.com/2022/01/10/a-simple-emf-detector-and-electroscope-you-can-make-from-junk-box-parts/ but the led stays on all the time on. Why? What could be the cause ...
Alex's user avatar
  • 121
2 votes
1 answer
586 views

Why does the emf depends on the material of the electrodes? Why is the emf independent of the distance between electrodes and amount of electrolyte?

Concise Physics mentions that: The emf (electromotive force)of a cell depends on 1) the material of the electrodes and 2)the electrolytes used in the cell.However it is independent of the a)the shape ...
Akhil Kumar Singh's user avatar
0 votes
3 answers
851 views

Constant Voltage Applied to Inductor

I'm seeking clarity on understanding what happens when a constant voltage is applied to an inductor. I gave this explanation in another thread and it was regarded as wholly misguided in the following ...
javamang's user avatar
-1 votes
2 answers
799 views

Inductor Back EMF Direction Relative to Changing Current

I have spent a lot of time thinking about Faraday's law and common explanation as given on wikipedia does not sit well with me. I may be confused. My concern is entirely with the wording of this ...
javamang's user avatar
1 vote
4 answers
1k views

Microcontroller 24V digital output

For a microcontroller generating a 20mA industrial digital output. What kind of setup is best? I'm considering: Microcontroller pin driving a low current N-FET to pull a 24V signal to ground. But ...
mosfeta's user avatar
  • 25
0 votes
1 answer
202 views

Wireless charging shielding requirements

I have a project where I want to throw a charging coil into the wonderful mix of tiny parts but the problem is, I also need an accelerometer/magnetometer roughly right beside said coil. I believe I ...
OwenTheProgrammer's user avatar
8 votes
3 answers
2k views

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 ...
menr1232's user avatar
9 votes
4 answers
1k views

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 ...
PersonWithName's user avatar
0 votes
0 answers
158 views

Identifying strange readings from Arduino EMF detector

Intro and knowledge self assessment Full disclosure, I'm an amateur, and my knowledge of electronics is cursory, and I'm more into computer science. But I bought an knock off arduino kit, and decide ...
user293815's user avatar
1 vote
4 answers
1k views

Motor Noise Reduction + PWM

I'm trying to suppress EMF coming from a brushed DC motor that I am running. I've tried using 0.1uF capacitors across the motor leads as discussed here: https://www.pololu.com/docs/0J15/9. It works ...
Celongar's user avatar
0 votes
1 answer
114 views

Is it normal to have around 40 V in your body, when touching your plugged, ungrounded laptop?

I have had bilateral shoulder pain and then both arms and hands pain for around 7 mounts, which got much worse when I started working from home, with my laptop. The ultrasound of shoulder muscles ...
Reza-sh's user avatar
0 votes
3 answers
168 views

Do switches induce voltage spikes in the AC power grid?

I know that DC inductive loads create back EMF when turned off and that's why we use a freewheeling diode. Does this also true for AC inductive loads and AC loads in general? I know we can't use a ...
John Cortex's user avatar
1 vote
1 answer
66 views

Isn't the voltage reading in this image wrong?

The conductor is moved from top to bottom through the B-field. Shouldn't the reading be negative on the volt-meter? Right-hand-rule gives that the positive charges experience a force towards us. Then ...
Clone's user avatar
  • 285
2 votes
2 answers
419 views

How is it that the induced EMF in an alternator is in quadrature with the main flux?

Looking at the simplified diagram of an alternator, the flux "linked" with the conductor is maximum at 90, 270 degrees, is also when induced EMF is maximum. So isn't the main flux in phase ...
User's user avatar
  • 849
-1 votes
1 answer
456 views

A misunderstanding with Faraday's experiment with iron ring

I am learning about electricity and magnetism, and have got some misunderstanding about Faraday's experiments with iron ring. If iron can conduct electricity, why is electricity inducted only while ...
Vasilly Fedorov's user avatar