Questions tagged [induction]

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350 questions
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What would happen if i move a rectangle shaped conductor in a magnetic field?

I know that in situation II there will be a induction current; and there will be no induction current because of the constant magnetic flux in situation I; but when we move a linear conductor in a ...
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Inductors in a.c. circuit problem

As written in my book and as I saw on some videos about inductors that in an ac circuit if an inductor is connected with an a.c. source then the induced emf would be the same voltage as the source ...
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I'm studying the principle of reciprocity for the MRI. At some point during a calculation the book states that: $$\oint d\vec{l} \cdot \left[\int d^3r' \frac{\vec{\nabla'}\times\vec{M}(\vec{r}')}{\... 1answer 441 views Do transformer follow Ohm's Law? We khow that due to Ohm's Law, I is proportional to V So if V rises, I should rise too. But in a transformer when V rises, I lessens. Why does this happen? It seems like transformers ... 0answers 332 views What is the physics behind the vibrating feeling you get when you touched an inducted metal surface? When I was last working on the highway, I stopped to help a motorist parked under high tension power lines. I'm driving a large Ford Transit van, fairly box shaped. My van was parked 90 degrees (... 1answer 153 views Why does a Crookes tube work when connected to an induction coil? From reading the answer below (regarding the mechanics of an induction coil) and the wikipedia article, it is clear that induction coils produce AC. However, the following excerpt from the "Crookes ... 1answer 81 views the conservation of the Electric displacement vector Good day everyone! Consider that we have the following capacitor ( look at the image bellow) that is partially filled with 2 dielectrics with a relative electric constant of er1 and er2, and we have ... 1answer 889 views induced charges inside a capacitor with two dielectrics consider that we have two dielectrics inside a capacitor as shown in the picture, let0s consider also that Q is the charge of the capacitor and d the distance between the two plates , the first ... 0answers 56 views What is the range of the validity of the Maxwell-Faraday equation? Similar to the question about the range of the validity of Coulomb's law, I am looking for references to literature that investigates the emirical bounds of the Maxwell-Faraday equation. However, it ... 1answer 75 views Why is the change in flux in Faradays law proportional to the area enclosed by the wire rather than the wire area perpendicular to the magnetic field? When deriving Faraday's law in high school physics the change of the area enclosed by the loop of wire is said to be proportional to the change of magnetic flux in Faraday's law. Intuitively, it makes ... 1answer 299 views How eddy currents effect the impedance of source? When we connect a bigger resistance to a transformer, the current decreases both in the primary and secondary. To be able to maintain the same current, we'd have to increase the voltage. Now imagine ... 2answers 311 views LR circuit with DC voltage In a LR circuit connected with battery what happens if R=0 assuming the switch is closed at t=0? Will emf be induced in the inductor? I am confused so please help me. 1answer 303 views How do Eddy currents follow conservation of energy? When wind blows, leaves of a tree move and they gain kinetic energy. In this case air molecules loose kinetic energy and transfer it to the leaf. But In case of eddy currents moving inside a conductor,... 1answer 804 views Does a wire/rod moving through a magnetic field have any change in flux? I know that if we move a rectangular wire from no magnetic field to through a magnetic field, there would be an induced voltage because there is change in flux (b∆x). However, if we moved a wire/rod ... 1answer 57 views If an inductor has current flowing in only one direction, does the magnetic field still vary directions? My understanding is that in a standard AC inductor the magnetic field in the core changes direction as the current through the primary coil alternates. What if the current through the primary coil was ... 2answers 377 views Why will a magnetic field cause a ring to hover? I was attempting a homework question which went like this: Where the crosses indicate a magnetic field in that rectangular region pointed into the screen, and we're asked which of the rings would ... 1answer 67 views How can a magnetic field exist outside a capacitor where the electric flux is not changing? I came across a line stating that a magnetic field exists in a region outside a circular plate capacitor that is being charged. I am not able to understand this as there is no change in electric flux ... 1answer 37 views Getting more out of less? [duplicate] So, I know this is a highly debated question... Okay so, can you use an Induction Motor to run two modified alternators at the same time, with one of them running the Electromagnets in the Induction ... 1answer 82 views Why would a steel tube vibrate under high voltage? Can anyone explain why a vertical steel tube, standing with one end in contact with the ground under a 230 \space kV electric transmission tower, would physically vibrate at high frequency? I'm not ... 1answer 364 views magnetically induced current density Given a material with electrical conductivity \sigma and an electric field E, the current density in the material is$$ J = \sigma E. $$Now assume that in addition there is a magnetic field B, ... 1answer 509 views Straight wire with constant electric current and square loop in the gravity field I was trying to solve this exercise but I found some difficulties in the proposed solution... The text is: A square loop of wire (side l, mass m, resistance R) lies on the xz plane, below a ... 1answer 390 views Charge inside spherical shell with dielectric between plates [closed] I'm asking help for this exercise. Charge q is surrounded by two thin spherical conducting shells C_1 and C_2. The space between C_1 and C_2 is filled with dielectric of constant k. If ... 1answer 81 views Inducted charge on a grounded sphere by a square of electric charge Consider a grounded conductive sphere with radius of a surrounded by four lines of charge of 2a length and charge density of D(C/m) each. What will be the inducted charge on the sphere? I was ... 1answer 188 views How is current induced in the coil in NMR? In nuclear magnetic resonance some current is indeced in the receiving coin by the rotating magnetisation vector. The current is associated with some energy. From where this energy come from since ... 1answer 276 views Finding the induced current in a loop and force acting on the conductor The conductor has a velocity to the right and is part of a closed loop (see the picture). Find the direction of the induced current and the direction of the magnetic force on the conductor There must ... 1answer 278 views Finding the direction of an induced current, swinging pendulum The conductor shown in #1 is held still in position #2. The switch s1 is now open, and the switch s2 is now closed, see #1. There is no current going through the conductor as its held still. Then, the ... 2answers 357 views Distance independent Coulomb's Law According to Coulomb's Law we know that the electric force between two bodies becomes weaker on increasing the distance. We also know that a charged particle attracts a neutral body phenomenon of "... 1answer 44 views Currents in circuits I know how to find the currents as functions of time when I have various circuits involving inductors, resistors and capacitors. Like for instance, if I have the following circuit: Then I have 4 ... 1answer 126 views How to calculate the dissipated energy on a wire as a function of x [closed] I am having some trouble solving this exercise, I would really appreciate if you could help me. Sorry if this has been asked before, I am new to the site and don't understand how things work here very ... 2answers 1k views From Lenz's Law to Faradays Law Relation Is there a way to mathematically describe how one gets to the minus in Faraday's Law from Lenz's Law? 1answer 87 views Contradiction in Faraday's Law? Let's consider a square loop of wire of edge length 1 inside a variable magnetic field such that  \dfrac{dB}{dt} = k . Faraday's Law tells that$$ \mathcal E = -\frac{d(BA)}{dt} = -A\frac{dB}{dt} =...
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Faraday's law needs a closed loop $\partial\Sigma$ in order to be applied (so as to be able to calculate the magnetic flux across $\Sigma$). However, $\partial\Sigma$ is just, at least according to my ...
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Can induced current in a transformers magnetic core be a good thing?

I've read that the magnetic core can be made from resistive (to current) but magnetic materials, and that the iron silicon sheets are laminated to reduce current in one direction. But wouldn't ...
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Can inductance ever vary with current?

Question is just as above. My thought is that since resistance of a material can vary with current (in a non-Ohmic conducter), is it possible for inductance $L$ in an inductor to vary for different ...
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Induced Current and Force

I am preparing for an exam in electricity and magnetism, and I came across this problem in my book with a solution that confuses me: A conducting loop of wire is initially around a magnet as shown ...
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What is 'arcing' at switch contacts in LR circuits when current changes instantaneously?

I am studying from Neil Storey's Electronics book and I can't understand the following paragraph: "We know that the current stabilises at a value of V/R. If the switch is now opened, this would ...
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Magnetic field generated pointing upwards, what direction is induced current?

In this Crash Course video, from 5:57 to 6:15, I think the directions are mixed up, but I could be wrong. She says that when moving the magnet into the loop, the generated magnetic field is pointing ...
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Can induction coils heat air?

I understand that induction coils can heat up conductive materials such as metals, but I'm wondering if they can heat up normal air. And if they cannot, can ionizing the air beforehand allow it to be ...
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Troubleshooting Kelvin's Water Dropper

I am attempting to replicate Lord Kelvin's Water Dropper and cannot seem to get it to generate a voltage. I am not concerned about the spark right now. However, when I fill up the reservoir with ...
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Which coil configurations transfers the most magnetic flux?

So i'm working on a home project that involves magnetic coupling. I was wondering, of the two configurations described bellow, which one would should allow the secondary coil to receive the most ...
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The trouble with EMF induced in the coil of wire

For anyone viewing this question who is not familiar with the notion of Induced EMF in the coil of wire let me briefly explain what i understood by it. EMF is induced inside a coil of wire whenever ...
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Current induced in loop moving out of magnetic field : contradiction using Fleming's right hand rule

In the picture shown magnetic field exists into the plane (denotes by the X) and the loop (iii) is moving out of the region of the magnetic field. According to Lenz's law, the induced current will ...
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Why does magnetism move electrons in a conductor?

What is to account for at the atomic level which gives magnetism its force upon electrons in a conductor? Why does the Lorenz force work?
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On electromagnetic induction. Does larmor precession cause electron flow in a conductor?

What is happening at the atomic level which makes it necessary for a magnetic field to be changing with time in order to induce an EMF in a coil of wire? Why won't a constant magnetic field induce an ...
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Need help understanding electrostatic induction in regards to the 'Thompson (Kelvin) Water Dropper'

...Aka the Kelvin hydroelectric generator, the Kelvin electrostatic generator, or Lord Kelvin's thunderstorm. Let's start with 2 metal cups, one above the other, in such a way that the top cup can ...
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What happens at during the transition of solid to liquid in a magnet?

So I just watched this video; https://www.youtube.com/watch?v=8i2OVqWo9s0 and I did a little looking through my physics book, and online, but I couldn't find an answer that explained it in simple ...
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Voltage generated in moving wire

hyperphysics: When a conductor moves through a magnetic field, there will be a generated motional emf. This is one example of Faraday's Law and it arises from the magnetic force. I don't ...
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Induction heating

An induction cooktop has a high frequency power source that is applied to a coil. I was wondering if you could take the high frequency electronics on a cooktop and instead of a coil take a 30 or 90 ...
Using $$F_\text{magnetic} = (BIL)_\text{wire} = (BQv)_\text{particle}$$ we can say $F\propto v$ as $B$ and $Q$ are presumably constant. Is the magnetic force proportional the radius, or distance, ...