Questions tagged [electromagnetic-induction]

Filter by
Sorted by
Tagged with
0
votes
1answer
89 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 $$ ...
0
votes
1answer
36 views

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 ...
0
votes
0answers
16 views

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 ...
0
votes
1answer
116 views

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, ...
2
votes
1answer
51 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 ...
1
vote
2answers
88 views

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 ...
2
votes
2answers
75 views

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 ...
0
votes
1answer
46 views

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 ...
0
votes
0answers
142 views

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 ...
10
votes
2answers
961 views

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 ...
1
vote
0answers
29 views

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. ...
1
vote
0answers
25 views

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 ...
0
votes
0answers
40 views

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 ...
0
votes
1answer
42 views

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?
0
votes
0answers
45 views

EM Induction in non-uniformly conducting ohmic toroid, thought experiment

Assume that there's a conducting toroid with radius of revolution $R$ and an own radius of $D$ so that the cross section of the toroid is given by $\pi D^2$ Assume that there's a circular region of ...
0
votes
2answers
34 views

Induction coil varies voltage

I was recently given this question by a friend as part of her homework: The gist of the question is: Say I have a laboratory induction coil with a primary coil which I can slide in and out of the ...
2
votes
2answers
139 views

Now what will happen in this circuit?

Consider a circuit as shown in this figure below- Assuming switch S1 is closed such that current flows in loop ABCDE for a long time and steady state is reached. Now, my question is simple, suppose (...
2
votes
0answers
377 views

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 ...
0
votes
1answer
45 views

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 ...
0
votes
4answers
65 views

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}\...
0
votes
2answers
153 views

Why is the integration constant in a purely inductive AC circuit assumed to be zero?

While studying about AC circuits, I came across the usual differential equation of an AC circuit (in which the voltage across the source is a sinusoidal function of time) containing an inductor only. ...
27
votes
2answers
4k views

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?
0
votes
1answer
23 views

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?
1
vote
1answer
26 views

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?
2
votes
4answers
373 views

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 ...
0
votes
3answers
229 views

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 (...
0
votes
4answers
76 views

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 ...
0
votes
1answer
32 views

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....
1
vote
0answers
14 views

How to calculate the limits for volume and mass for induction heating samples?

I'm evaluating the feasibility of using volumetric induction heating to quickly heat up steel molds. One thing I have come across is that induction heating really only works for surface heating or for ...
3
votes
1answer
113 views

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 ...
1
vote
0answers
49 views

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 ...
0
votes
1answer
46 views

Is Faraday's induction principle applicable in outer space?

Is it possible for an AC generator to actually generate electricity let's say being in a ship orbiting Mars or on the surface of the moon? Does Faraday's principle require the magnetig field of the ...
1
vote
1answer
86 views

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 ...
-1
votes
1answer
124 views

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:
2
votes
1answer
43 views

Electromagnetism— why do we only care about flux inside the loop? In other words, why is the area in 'φ=AB' the area bounded by the loop?

When we calculate the emf induced by placing a loop of wire inside a changing magnetic field, why do we use the area bounded by the loop to calculate total flux and then the rate at which it changes? ...
0
votes
0answers
259 views

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 ...
0
votes
1answer
215 views

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 ...
1
vote
1answer
84 views

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 ...
1
vote
1answer
103 views

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 ...
-1
votes
2answers
58 views

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.
0
votes
2answers
57 views

How is it possible that the two voltmeters in parallel measure these different voltages

I'm currently studying induction law and circuits with inductors. I came however with the following circuit: Now my text says the following: "Unlike what your intuition might tell you, oscilloscopes ...
1
vote
1answer
175 views

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 ...
0
votes
2answers
721 views

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 ...
1
vote
1answer
26 views

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?
0
votes
2answers
54 views

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 ...
0
votes
2answers
74 views

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 $A$, $I_A$, ...