Coil Definition and 864 Threads

Hi, having difficulties in this problem. Looking for ideas. For now, I think the combined voltage of source and coil should be bigger or equal to EMF, for the battery to get charged: ##U+L\frac{dI}{dt}\ge EMF## the current going through the coil, I think, would be...

TL;DR Summary: Determine the wet bulb temperature of air entering a room when the dry-bulb temperature is given. This is the hardest HVAC PE practice problem I've attempted. Can someone show me how they would approach this? The goal is to find Twb leaving the cooling coil as shown in the image...

I assume that electric current is made up of moving electric charges. If this hypothesis is correct, then the current that flows through a coil is made up of accelerated charges. I am not interested in evaluating the situation quantitatively. My question is conceptual. Does a coil that conducts...

I have a fuel pump consisting of a solenoid coil. I have tested the fuel pump at 12V supply. The pump actuates at 20% duty cycle(200Hz frequency) and draws a current of 1.7A. When I increase the supply voltage to 24V it actuates at 7% duty cycle(200Hz Frequency), drawing a current of 0.6A. How...

Hi everyone . I need help on the following problem. I built a current sensor that is based on the same principle as the Rogowski coil. Don't propose other alternative methods to measure the current because its application will be different and I don't want to talk about this. in reality what I...

Hi, This is not a homework problem, but a small personal project where I am looking to create a small solenoid that can create enough pushing force of approximately 0.5 lbs. I am wondering what the best route is to create this amount of force. So far, I was able to lift about 32g with my...

Hello, Knowing that the loss cone for a symmetrical geometry is also symmetrical, I was thinking has anyone ever tried a magnetic mirror where the central magnets are circular but the end magnets that create the highest B field are instead flattened. Wouldn't a flat coil achieve a stronger B...

TL;DR Summary: Forces on Elliptical Current Carying Loop Please consider Current carrying elliptical 1-turn coil as shown in the picture. Is it true that due to forces from the current , the elliptical shape of the coil will tend to become circular ? Thank you...

My answer is (B) but the answer key is (A). My working: $$\varepsilon=-\frac{d\phi}{dt}$$ $$=-AB\frac{cos\omega t}{dt}$$ $$=AB\omega \sin \omega t$$ Why the answer is zero? I thought the flux will be zero, not the emf. Thanks

I use FLHR and the plan diagram. This suggests that the left hand side of the coil is going down. I have added annotations to this, which agree with the mark scheme which then goes onto suggest that the coil turns clockwise. To me though this would make it go anti clockwise. So... what am I...

Hi what factors determine the resistance and inductance in a coil and they related i.e. if the resistance is high would the inductance be high ? Additionally, would the resistance and inductance value change over time? I only ask this as we tested the resistance and inductance on our coils...

Hello! I have a question regarding the mutual inductance of two coils in a transformer. In the formulas for linked coils ##M=k*\sqrt{(L_1*L_2)}## where ##k=1## for a perfect coupling. I wanted to check my understanding about mutual inductance and see how it can be determined. When I vary the...

What is the difference between a current-carrying coil and a solenoid?

Hi guys, I'm new to this forum. I'd like to know how I could perform a simulation to find the induced EMF in a coil placed closer to a current-carrying conductor. I'm not sure how I should model the coil. I tried modelling it as a solenoid but the solenoid exceeds my required length when I enter...

Playing around with electricity and magnetism. Well, trying to anyways. Wound some wire up and down the length of a 4" screw several times. Thought when I spun the magnet close to the coil I would get a detectable amount of current on my voltmeter. Anyone know why I'm not reading anything? I...

While thinking about back EMF I stumbled upon a curious question. We know that whenever a coil/conductor that passes current is switched OFF and the current is stopped it never stops immediately but instead has a type of "inertia" where the magnetic field created by the current as it passed now...

Hello all, I am currently studying for a physics a-level qualification in the UK, I use the AQA specification and I am having trouble understanding this image representing a scenario I found in my textbook. The first image in the three part diagram shows this rotating coil and to me, it makes...

Hi everyone. there are materials called soft magnetic and they are halfway between a permanent magnet and a ferromagnetic material. I would like to try to make a field coil loudspeaker where the maximum amount of flux-density is very important but also the amount of current it takes to create...

Hello, I am wanting to wrap a coil of wire around a tube, suspend an iron cylinder in the tube, energize the coil, and have it be able to suspend around 500 pounds on the iron cylinder. I was playing around with some online calculators for coils, and didn't really get anywhere, so I figured I...

Maybe a not well thought out question: https://cdn.automationdirect.com/static/specs/78relays.pdf 781-1C-24A Relay is listed as having ##177 \Omega## Coil Resistance. I'm assuming that figure will give the Real Power dissipated by the coil (entire relay circuitry) for some current ##I##, or...

I want to ask about part c (iii). This is what I did: max e.m.f produced = NBAω = 32 x 0.074 x 4.8 x 10-2 x 2.4 x 10-2 x 2π x 9 = 0.15 V But the answer is 0.077 V so my answer is off by factor of two. Is my mistake related to "emf produced across the side of AC of the coil"? Thanks

So I'm familiar with the magnet falling through a copper tube demonstration that shows the induced magnetic fields slowing the magnet down. I know that this experiment is also possible with a conducting coil as long as the coil forms a closed circuit. I'm trying to find a way to calculate the...

A DC supplied superconductive electric coil must give off EM radiation according to Maxwell's law because rotation is acceleration. Does it?

My answer is when the small coil is rotated, there will be change in magnetic flux in it. Initially (before rotated), the trace in c.r.o will be sinusoidal. After it is rotated, the trace will still be a sinusoidal (but I am not sure whether the amplitude will be the same). But the answer key...

I'm trying to simulate a Magnetostatic problem. In my model there are two coils and a reciprocating permanent magnet. I defined a parameter, Xpm (movement of permanent magnet) in x direction to imply the reciprocating movement of permanent magnet like a piston. Xpm = f(t). I defined "t" as sweep...

Hi Guys, I am doing a Maxwell 3D&Icepak thermal simulation for a air coil. I want to get its temperature when loading 1.6A current. So I use Eddy Current type in Maxwell 3D and Temperature and Flow type in Icepak. Then I load 1.6A solid current and adaptive frequency of 800 MHz for the coil...

Summary:: . Hi ,so am currently doing homework , and was wondering if anyone could tell me if i have done my calculations correctly ,because am not 100% sure that i have answer to those 2 questions correctly .If i have went somewhere wrong if you could tell me where and how i could fix it...

The amount of power generated by a coil in a changing magnetic field is determined by the area perpendicular to the field, the field strength, and how quickly those values change over time, and is multiplied by the number of loops in the coil. But that made me wonder what would happen if one...

I need to find the FEM induced in a coil that rotates around the y-axis and is inside a solenoid. The coil starts in the plane yz ##r## is the radius of the coil ##n## is the number of spiral by length of the solenoid. ##N## is the number of turns of the coil ##w## is the angular velocity that...

I would like to know how to calculate, for any specified frequency in Hz, the required diameter of a 90 degree phased, quadrature coil array such that its generated EM field achieves rotation at the speed of light. Could someone please provide an example of the calculation using a specific...

The question I'm in doubt about is The motor coil has a resistance of 10 Ω and is powered by a voltage of 120 V. When the motor is operating at rated speed, its emf is 70 V. Thus, it is questioned: a) What is the coil current when the motor is started? b) What is the coil current at rated...

Hello, am kind of new to all the physics stuff , and kind a terrible at maths but am trying my best to be good at it one day .So i was told to answer this question When a direct current of 2A is passed through a coil, the potential difference across the coil is 20V. When an alternating current...

I am trying to understand the reaction of a steel coil compression spring when pulsed. The spring I am interested in has the following physical characteristics: k (spring constant in pounds per inch) = 2.88 d (wire diameter in inches) = .043 n (number of active coils) = 29 D (mean diameter of...

I've been told that if you drop a magnet through a coil the induced emf and flux graphs would look like this: I understand that when the bar magnet is in the middle of the coil the emf induced is zero as flux change in top and bottom is in opposite directions but why is effective flux maximum...

I'm trying to complete this past exam paper Q. Water volume = 200hl = 20000L 1L=10^-3 m^3 20000L = 200 m^3 Density of water at 15 deg C = 999 kg m^3 Density = Mass/Volume 999 kg m^3 = Mass/(200 m^3) Mass of water = (200)(999) = 199800 kg Heat required to to heat 199800 kg water: Q =m C dT =...

So my idea was that to reach the equilibrium position, the final moment of force has to be 0 (so in the end the forces will “eliminate” each other). And I found the equation Fm=B*I*l*sinα, which should characterize the force, which affects wire with the current in a magnetic field, and Fleming’s...

The experiment consists of a large field coil (connected to a current source) surrounding a coplanar and coaxial small detector coil in the center of the field coil connected to the oscilloscope. 1. Matching Current v. Time Graphs to Oscilloscope Graphs Example of one pair of graphs (I'll...

I'll try to explain to you my thinking behind this problem... tell me if it's correct or not. In short, I have assumed the area enclosed between the wire and the left side of the coil to be ##A## in which is present a ##-\hat{z}## field, and noticed that the flux it generates must be canceled by...

I managed to solve this problem by writing the total E.M.F. as the sum of the one which would have been induced with only the magnetic field varying(and constant ##A##), and that with only the area varying(and constant ##B##). However, I got to this solution(which doesn't totally convince me)...

It is long known that the toroidal field alone is not sufficient to achieve toroidal force balance within a tokamak due to the field being bent and geometry restricting the field to be of even strength both within the inner and outer circumference of the ring. Induced current is thus used for...

Assume a solenoid coil(made up of ##N## windings) placed in the horizontal(##\hat{y}##) direction and in a constant uniform magnetic field. Would an induced current run through the(closed) coil if it spins around its central horizontal ##\hat{y}## axis? My guess is "no", since such a current is...

The present setup is a step-down transformer. Im thinking if n1 is decreased to match or be less than n2, then it will be a step up transformer. so A. (but answers say B)?

So voltage is 12v the coil is 80 watts

Attached is a photo the the primary transformer coil of a QI (I believe pronounced CHEE) wireless charger, as used for charging a cell phone. I know the fields of solenoids but what would be the magnetic field structure of this. By-the-way, a similar coil was used on old AM radio sets.

Hi. At school, I once worked with a Teltron tube that looked very much like this (I don't remember the brand): The electrons are emitted from a coil that must be heated with a voltage around 5 V. But for some reason, it must be AC, it doesn't work with DC (and it took me a long time of...

My answer will be no for both (a) and (b) because there is no change in magnetic flux experienced by the circular coil. Am I correct? Thanks

I want to understand the direction of force on the voice coil, if the conductor is straight line it is easy to find the force direction. In the case of the diagram i shown below, for the curved surfaces i should take tangential to the surface at every point. Am i correct? So for position 1 since...

Surely a tough one, I am doing it from the basics. This is the diagram i tried to draw showing the Force and current I The Length L is the tangent to the circle. The Force F is pointing upwards at ##90 Deg## to the ##\vec B## and also perpendicular to ##\vec L##. I am considering a small...

The near-range magnetic field ##\vec{B}## of a point charge ##q## at distance ##\vec{r}##, moving at a non-relativistic velocity ##\vec{v}##, is given by $$\vec{B}=\frac{q}{4\pi\epsilon_0c^2}\frac{\vec{v}\times\hat{r}}{r^2}.$$ Faraday's law of induction for the induced EMF ##V_c## in a coil...