Questions tagged [emf]
The emf tag has no usage guidance.
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1answer
58 views
DC Shunt Motor Load Loss
I have three DC shunt wound motors in series. Each motor has a coupling to a transmission. I am trying to work out (mathematically, as opposed to intuitively), what happens if the coupling was to drop ...
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2answers
84 views
How do I connect a four way key in a potentiometer?
I asked this question in Physics stack exchange and had an answer, but I couldn't understand it well. A comment said this stack exchange was a better fit for the question.
Question:
How do I connect ...
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0answers
49 views
Why aren't homopolar generators more commonly used?
In particular with the advent of HVDC(high voltage direct current). Using mercury(metal), the resistive losses can be greatly reduced. There has even been some experimental research into neon plasma ...
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1answer
52 views
What happens in a generator so that we get a sinusoidal voltage as an output?
I read this online, " For a travelling magnetic field in a circle, the induced magnetic field in the armature of the generator will be sinusoidal. That's why the generated voltage is a sinusoid, ...
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1answer
80 views
Are headphones with EMF measurement of 10,000 milligauss harmful to me?
I used a EMF detector app on my phone and measured the EMF output on my wired headphones. It measured around 10,000 milligauss on one part of both ear cups. Since wearing these headphones on my head ...
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3answers
102 views
What is the SI unit of magnetic force?
As derived from F = qvB sinθ, what is the unit of magnetic force, and why?
Edit: I mistakenly asked about magnetic field before. -- I'm asking the magnetic force.
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1answer
56 views
EMF from power lines [closed]
My new house flat is near an overhead power line. It's a steel structure so it's the higher energy lines. The line is about 1200 feet away at the closest point, I guess that is fairly far and you'll ...
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1answer
151 views
Calculating a voltmeter reading
I'd like to preface with saying that I'm quite new to this.
Given emf E = 9 V, and that both resistances are equal, R = 1 kΩ, ...
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2answers
95 views
Strategies to reduce EMF radiation
During a long-term, almost six month long, data acquisition in a proximity of scanning electron microscope I have found a significant source of magnetic field noise, which is altering the results. I ...
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1answer
79 views
Stepper Driver signal noise problem (Ground Loop)
I have an BluePill board (Arm Cortex M3 Dev. Board). Also a a4988 stepper motor driver. BluePill is powered from usb of my PC. Stepper motor driver is powered by external power supply which is 220V -> ...
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1answer
67 views
PC monitor flickers/resets when washer motor switches on or off [closed]
My room is next to our laundry and I've recently got a new PC monitor. I've noticed each time the motor in the washing machine is switched on or off, my monitor flickers/resets. The monitor is 32" but ...
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1answer
42 views
Cancelling Ripple With A 7555
Friends, I did this once but don't remember the detail. A very sensitive circuit which switches a relatively heavy load. I used a 7555 IC to momentarily blank out any ripple or instability caused by ...
6
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1answer
114 views
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 ...
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0answers
44 views
EMF - DC Permanent Magnet Motor
I am using FEMM to design a dc permanent magnet rotor.
I am trying to calculate the EMF that is induced to the rotor. Since each coil has a different position, the induced emf will be different.
In ...
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3answers
161 views
Circuit approximation of Induction in guitar pickups
I was trying to learn the way basic guitar circuits work, the other day, and I stumbled upon a thing that I couldn't fully understand.
According to this site, a simple guitar circuit can be made as ...
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1answer
29 views
What is the canonical form based on sinus of the autoinduced EMF in a coil
I am stuck with this exercise as I can't really find the expressions I need in order to solve this. Please help me & guide me theoretically, so I can finish this.
Deduce the canonical form based ...
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1answer
36 views
Using 2 Tank Circuits to Determine the Position/Direction of a Wire
I am building a robot that uses 2 LC tank circuits with some gain and analog filtering to determine the position of a "Track Wire" that has an AC current of a specific frequency traveling vertically. ...
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2answers
381 views
Zener diode for solenoid
I am new in electronics and this is old subject but still. I started new Arduino project where I control 4 solenoid valves independently via Arduino 4 chanel 5 V Relay module. From the beginning I put ...
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1answer
99 views
A simple motor using Copper coil
This is a simple motor made with a magnet, a battery and a copper coil.
I am curious to know how can it be explained using physics.
I know that the copper is diamagnetic but not enough that it can ...
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1answer
170 views
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 ...
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2answers
890 views
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, ...
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2answers
59 views
Using an analog temperature sensor near 3-phase 150V , 40A Motor Controller?
I'm looking for suggestions on what type of temperature sensor to use. I need to have it attached to the heat sync of a 150V, 40A 3-phase motor controller. The motor controller is in a enclosed space ...
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3answers
83 views
Question about coil emf
Hi I am a Korean student studying physics. Recently I was solving a physics problem about coil emf and I have a question.
As you see in this circuit and the graph, when you close the switch the emf ...
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1answer
104 views
Question about Stepper Motors
I have a need to sometimes manually turn the lead screw on a stepper motor controlled CNC system (which I have not purchased yet). So IF I put a switch in the wires of the stepper motor and open the ...
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2answers
835 views
Relating DC motor with the Fleming right hand rule
I am studying DC motors and I know that what the direction of the rotation will be given by the left hand rule.
If I compare the right and left hand rule, if I point the thumb and the first finger ...
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3answers
451 views
AC Circuit Having Only Capacitor
In my book, it is written that at any instant,
PD across the Capacitor Plates = Applied EMF ---------(1)
Assuming that it's a pure Capacitor of Capacitance C, I think if Voltage across Capacitor ...
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0answers
82 views
Are the measured values in the EMF meter are peak values or average?
EMF meters are usually measure the AVERAGE power flux density(w/m2) of the RF frequencies(at high frequencies),while measure the PEAK field intensity(v/m)of the same RF signals(usually burst signals).
...
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3answers
1k views
basic differences between voltage and emf?
what are the basic diff between the emf and voltage?
is it that the voltage of a battery is emf and voltage is potential diff between two points,and also please give me some suggestion how to take ...
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3answers
1k views
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?
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5answers
2k views
“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 ...
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2answers
80 views
Why is the outlet ground voltage different from grounded Macbook voltage
Measuring on A/C with a digital voltmeter:
Measurement One
I connect the ground lead to earth on a 3-prong plug,
And hold the other lead with my thumb and forefinger,
And observe that I register ...
1
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2answers
120 views
Electromotive force of a battery
The definitions of electromotive force of a cell that i have studied include:
1.When no current is drawn from a cell,i.e., when the cell is in open circuit, then potential difference between the ...
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1answer
63 views
Measure EMF Radiation from High Altitude Balloon
I'm participating in a competition which involves building a probe that will be attached to a weather balloon. It will probably rise up to an altitude of 30 km.
I am thinking of measuring EMF ...
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1answer
653 views
RC filter in a simple PWM motor drive
I was looking at a friend's design for a simple PWM motor drive and I'm trying to figure out what's the use of some components. Here's the schematic:
I get what most parts are for:
power supply
fuse ...
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3answers
79 views
DC Motor EMF re-usage?
I have 2 questions:
1 - The Brushed DC motor variety has a type when one turns the shaft manually it free runs with no friction or resistance at all, and then another type which feels like a mild ...
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4answers
6k views
Reduce interference over 3.5 mm to cassette tape adapter
I have one of those cheap 3.5mm > cassette adapters, to use in my car. I've purchased high-end ones (around $40) and I've purchased cheaper ones like this ($20) but I always get static/feedback from ...
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2answers
1k views
Can ground plane EMIT noise?
I have 3 separate grounds in my project:
AGND - Analog ground is very quiet, very small relatively smooth currents
PGND - Power ground used for power bypass caps and power supply related circuitry is ...
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2answers
2k views
Induced EMF in a transformer
In a transformer a sinusoidally varying voltage is applied to the primary coil of the transformer which give rise to a time varying flux which induce another sinusoidally varying EMF in the primary ...
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1answer
343 views
Noise from stun-gun based butane torch ignition spark is locking up ATmega328 microcontroller
I have a stun gun (http://www.amazon.com/VIPERTEK-VTS-989-Heavy-Rechargeable-Flashlight/dp/B00FPE6UN2) which I am using to create a large 1/2" electrical arc through the air to remotely ignite a ...
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1answer
189 views
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 ...
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1answer
62 views
Produce current
Ok, so I was trying our an experiment to generate minute current. I got a battery operated gear motor which can produce current to light ant led bulb when rotated. I am trying to create an automation ...
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1answer
97 views
What electric field strength in the range 50MHz to 3.5GHz should be considered “natural”?
If we were to measure the electric field strength of the earth's surface in the range 50MHz to 3.5GHz (in the absence of any man-made transmitter), what value should be considered "natural"?
The next ...
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1answer
99 views
Can superimposed (combined) wireless signals create a health hazard?
Not to sound all tin-foil-hat-like but I'm learning about wireless signals and am trying to understand it better. So my question is:
When multiple wireless signals are transmitted at the same time ...
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1answer
64 views
Do external EMFs affect in some way a capacitor?
I Know that inducters are affected by external magnetic fields .The affect depends on the construction of the inducter . What I would like to know is how capacitors are affected by external ...
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1answer
71 views
Do short circuits between transformer windings cause noticeable change in EMF?
I am looking into developing a sensor system to be placed within a transformer. This sensor system in theory, should be able to detect any unprecedented change in EMF within the transformer enclosure.
...
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3answers
16k views
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 ...
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1answer
555 views
Can I tell the voltage of High Power Transmission lines by its Type?
I am moving to Foster City, CA and am looking at an apartment about 550 feet from these power lines: https://www.google.com/maps/@37.562322,-122.27068,3a,75y,153.58h,99.44t/data=!3m6!1e1!3m4!...
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1answer
501 views
additional resistance required to produce a potential drop
A wire of length 100cm is connected to a cell of emf 2V and negligible internal resistance. The resistance of the wire is 3Ω. The additional resistance required to produce a potential drop of 1 ...
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1answer
130 views
Why isn't number of loops included in the EMF equation?
The following is a snapshot from (http://www.electronics-tutorials.ws/inductor/inductance.html).
I understand the first equation which relates inductance, number of wraps, and current. But since EMF ...
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2answers
1k views
How do I reduce the Counter EMF?
I hope I can explain what I am asking.
We will connect a DC motor to a single phase rectifier. Motor will carry a load. And motor sould be able to spin right and left. And when it is changing its ...
