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Questions tagged [electromagnetic-induction]

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Electromagnetic induction due to a long copper tube [on hold]

What will be velocity time graph when a bar magnet is allowed to fall through long vertical copper tube?
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16 views

Current induced by permanent magnet moving along toroid coil

(It's not really shown in the pictures, but please assume that the coils are included in a closed circuit in both configurations. Maybe they could serve as a tension source in their respective circuit ...
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Resistance of a hollow cylinder [closed]

So there is a hollow cylinder with inner radius a and outer radius $b$ material is present between $a$ and $b$. its resistivity is $\rho*P$. Its height is $h$. A time varying magnetic field is present ...
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Conducting wire covered by a paramagnetic dielectric

How does the conductance of a conducting wire change if it is covered by a paramagnetic material comparing to a diamagnetic one? I am interested in the DC or low frequencies response mainly. For me ...
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Can an Opposing Current Create another Opposing Current?

In Inductors when current increases it's magnetic field induces a voltage which causes an opposing current that slows down the rise of the current that initially creates it, but can this opposing ...
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1answer
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Self-induction and conservation of energy [closed]

back EMF when switch is open is greater than back EMF when it is on; is that opposes the law of conservation of energy?
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1answer
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Sliding rod in magnetic field with two loops

The circuit is concatenated with a constant flux $B$ and the rod slides with constant velocity $v$. Find the current through the rod. Before I always solved the problem without the resistor $R_2$ by ...
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1answer
29 views

Why do we ignore the negative sign of self induction while considering inductors in an AC circuit?

I have been taught that the back EMF in a coil as per Lenz's law is $$ e =-L \frac{di}{dt} $$ Then why is that during circuit analysis of AC circuits, we consider the e across inductors to be $$ ...
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1answer
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Why is rate of decay of current in a coil greater than the rate of its growth?

In this experiment: Where neon lamp doesn’t light when the switch is closed because the voltage is much lower than that required to ionize the gas, but it only lights up momentarily when the switch ...
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Induction heating through a slightly magnetic material

Would be be possible to inductively heat a rod with with ~100 relative permeability enclosed in a tube with ~2 permeability? The gap between the rod and the interior surface of the tube is uniform ...
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1answer
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Can emf be induced by reducing the radius of a loop?

Faraday's law tells us, that the induced emf in a conducting loop, is equal to the change in magnetic flux per second through the area encircled by the loop. If we decrease the radius of the loop, ...
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1answer
39 views

Influence of Lorentz force on Eddy Current

A magnetic field exerts a force on a moving charge called Magnetic Lorentz force. How does this force work in case of eddy currents? The following is an extract from Wikipedia: "Another way to ...
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Scientific reason behind electromagnetic induction [duplicate]

What actually happens inside a loop when placed in a changing magnetic field that EMF gets induced across it? And also if it is connected and the direction of the magnetic field is changed then ...
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What does 'Oppose a Change in Current' really mean from Lenz Law?

We all know what Lenz Law is, but I have a bit of trouble conceptualizing the phrase above. Does 'Oppose a Change in Current' means it will take more time for the current to increase to its maximum ...
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1answer
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Why EMF induced in the coil acts to oppose any change in the magnetic flux?

This might be an absurd question for some of you guys. According to Lenz's Law an induced current will create a magnetic field that induces another current in which it opposes the current causing it ...
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Average induced emf of a AC generator

In my physics textbook, it says if a simple generator made of one coil rotates 180° from the position the plan parallel to the magnetic field lines equal 0 if the rotation from position ...
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2answers
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Why is there an induced EMF in a plastic ring?

If we were to pull a plastic ring across the boundary of a magnetic field, why does an emf form? If this was a metal ring I would fully understand because the electrons are free to move in a metal ...
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Conceptual question about Magnetism? [duplicate]

I am confused about Magnetic force whether it does work or NOT because i think that the battery does the word and the magnetic force only redirects the work done by battery into some displacement etc. ...
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In motional emf why doesn't the magnetic field due to the current in the moving rod exert force on the rod?

When a metal rod moves in a magnetic field an emf is produced across its ends called motional emf. When a resistor is connected across it a current flows through it.Due to this current a magnetic ...
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rotating capacitor question

Imagine a simple setup. I have a copper disc and another copper element held close to the disc at one of it's sides, this element is stationary but the disc is rotating, the part between the disc and ...
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Why do we need frequency of changing current for induced EMF?

I know that a constant current doesn't create induced emf, however, I do not know why a changing one does. Are there any ways to understand it briefly/easily, or is it just the way it is?
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Why are there two concave poles in an AC generator

If we suppose that the magnetic poles in the AC generator are regular rectangular bar magnets, then the field lines are supposed to be straight lines as in the photo below: And then the direction of ...
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1answer
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Can we use magnetic flux formula $BA$ for straight wire/conductor placed in uniform magnetic field

While coming across electromagnetic induction, I learned that for an emf to be induced in a coil of wire there should be a change in magnetic flux which is given by $\frac{BA\cos\theta}{t}$ where ...
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4answers
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Problem with faraday's law in a closed circuit with a battery: is there a changing B flux?

We know that in a closed circuit connected to a battery, $\oint E.dl\ne0$, due to the non conservative nature fo the EMF generated by the battery. But, according to Faraday's law, then $\int_{\Sigma}\...
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Please help identify this physics apparatus!

This was my grandfather’s and have no idea what it is only that it is some piece of physics equipment! The main black cylinder doesn’t seem like it wants to rotate but not sure if it should?
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1answer
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Electro magnetic field

If an emf is produced in a dc motor, would it be possible to use the motor somehow as a generator or source, taking power out of it rather than putting power into it? How might this be done?
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liquid metal induced current due to rotation in B field

My question is this, I have a hard time figuring out the outcome due to the geometry I assume. So I have a rotor, on the rotor sits a ring filled with conductive liquid metal, also on the rotor there ...
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1answer
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Does a magnet lose more potential when (passivley) magnetizing another metal?

Does a magnet lose more of it's magnetic potential when (passively) magnetizing a second (ferromagnetic) metal compared with simply being left alone for the same amount of time it took?
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4answers
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Maxwell-Faraday's Law of Induction Violated?

I am having much distress over Maxwell's 3rd Equation (Faraday's Law of Induction) and a thought experiment I had. Given that Maxwell-Faraday's equation is $$\oint E \cdot ds = -\frac{d\phi}{dt}$$And ...
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3answers
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Why does change in magentic flux decrease as turns increase?

Let us consider the primary coil of a transformer. As we apply a constant voltage (say 240V) over the primary coil, and vary the number of coil turns we should expect to see the below relation (...
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4answers
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Can Induced current be obtained by only changing the direction of the Magnetic Field?

According to Faraday, a change in magnetic flux induces current in a conductor. Just suppose we take a circular coil, and pass a magnetic field inside it, and keeping changing the direction of ...
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1answer
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How does the atomic magnetic moment get locked with external magnetic field?

When an atom has a net magnetic moment that is not aligned with external magnetic field, it is said that the atom rotates because of the torque and the magnetic moment gets aligned with external field....
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1answer
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Is there is any way to prove the Faraday's law of induction?

I want to know if there is any way to prove the Faraday's law or is it just an experimental observed phenomena? More specifically, is there any reason why the proportionality constant is 1? How did ...
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Magnetic field of a rotating superconductor - exists?

On several places (e.g. wikipedia superconductivity) people stay, that for superconductivity the resistance is exactly zero. The mass of electron is small, but for sure not exactly zero. Imagine a ...
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Why not change magnetic flux only at the edges?

I learnt Faraday's Law of Induction however I was confused about why the area aspect of magnetic flux impacts on the EMF generated. Why do magnetic field lines inside the coil area affect the EMF ...
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1answer
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Faraday's law intuition

I am trying to understand Faradays law of Induction. As far as I know when we are speaking about the E field we mean the field caused by charges(stationary or moving) whose value we can calculate by ...
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1answer
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Why is the emf induced in a closed spiral in a time-changing magnetic field less than that induced in a closed loop of the same radius?

I don't get it. Is the area linked different? Or is it something less? This is the kind of closed spiral I'm thinking of:
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why is $E=4.44fN\phi$ valid for the primary winding of a transformer?

According to the Faraday Law of induction, A variable magnetic field in a region induces an electric field in the same region. I have trouble applying this to the two sides of a transformer. For ...
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1answer
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Force by a changing magnetic field on a stationary charge

I already know that a moving charge experiences a force in a constant magnetic field governed by the Lorentz force formula. What I want to know is that whether a changing magnetic field exhibits a ...
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1answer
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Faraday's Law and the Law of Inertia

Faraday's Law can be stated qualitatively as : Any loop (of wire) opposes/resists the change of magnetic flux through it. The Law of Inertia states that any physical object resists its change in ...
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1answer
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continuous Electromagnetic Induction in two coils

First of all, i am sorry if i overlooked this question although i browsed the list of questions on the topic. I have difficulty understanding that when a changing magnetic flux in a coil induces an ...
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2answers
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Equation for induced electromagnetic field

Is the induced electromagnetic field (EMF) always equal to negative rate of change of flux, where $f$ is the flux? I'm curious how it can be true in every case.
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1answer
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Explain Lenz Law with Conservation of Energy [duplicate]

My question is: If the bar magnet is moved towards a coil connected to a galvanometer and instead of a opposing magnetic pole a attractive pole i.e. south of coil and north of magnet is created due to ...
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2answers
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Magnetizing inductance in transformer

I asked this question in electronics stack exchange as well but I thought it would also be applicable here as my question revolves largely around Maxwell's equations. I am learning about transformers ...
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1answer
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Electromagnetic Induction with liquid conductor

If a conductor is moved in a magnetic field current is induced in that conductor. So if I use Liquid mercury in place of the conductor will the same happen?
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2answers
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Predict the polarity of the broken coil

When the north pole of a magnet is brought near a broken coil, then the current is in direction, A toB . Now, the coil should behave as a battery such that two ends of coil are +ve and -ve. Which end ...
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2answers
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Is induced EMF proportional to the square of the number of turns of a solenoid?

In order for this question to be clear I must first give some context: Consider a 10cm long solenoid (solenoid A) of radius approximately 1cm with 400 turns. Let the current in $A$, $I_A$, ...
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3answers
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Voltage vs. EMF for a varying magnetic flux against an ohmic circuit

Suppose there is a circular wire, whose material is ohmic with uniform resistivity. If an increasing magnetic flux is applied to this "circuit", electric current will flow in one direction. Then by ...
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6answers
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Right Hand Rule?

I'm trying to determine what the correct right hand rule is, but Google isn't helping. I've seen three different versions of Fleming's Right Hand Rule now, and I'm very confused. Here are three ...
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1answer
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Usefulness of an iron core in a magnetic coil used to generate current

I wish to light a LED by moving a permanent magnet relative to an inductor consisting of a coil of copper wire. Can I increase efficiency (current produced for a given magnet motion) by using an iron ...