# Questions tagged [induction]

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351 questions
50 views

### Current Induction Explanation

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, ...
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### Magnetization and Demagnetization of an Inductor

when we apply the AC voltage to an Inductor the Average power over a complete cycle is zero. the figure in my book explains it. but I couldn't understand it, I could have directly asked the question ...
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### Why induction coupled plasma use RF frequencies?

The frequency I see all the time is 13.56mhz,I understand that when you want to make heat treatment surface finish on steel,you use high frequency in the heating coil so the skin effect heats only the ...
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### Field induced outside a grounded 2D circle conductor by an exterior point charge. A puzzle, not what you think!

A unit charge is placed outside a grounded conducting unit radius circle at the origin. What is the field outside the circle? This is not the obvious problem you immediately think it is. A classic, ...
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### Resulting magnetic flux in the core of a transformer

In a transformer, let's say we have: $I_1, I_2$ - currents through the primary and secondary winding $V_1, V_2$ - voltages $N_1, N_2$ - number of turns $F_1, F_2$ - magnetic fluxes through core, ...
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### Relation between Maxwell's equation and faraday law (conservativity of electric field)

So, i have one question about how the induced electric fields will be either conservative or not. So, first of all, we got Faraday-Lenz's Law: $$\epsilon = - \frac{d\phi}{dt}$$ This only refers to ...
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### Why can induction cooktops not use aluminium or copper utensils?

Why can induction cooktops not use aluminium or copper utensils, when both materials are conductors and hence conducive to eddy currents, which are used by these devices to cook? Edit 1 (10 Nov 2016):...
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### Induced emf in ring in magnetic field

A metal ring is placed in a magnetic field. The ring has a gap in it though. As it falls through the magnetic field, is it true that it still experiences an induced emf and eddy currents but not a ...
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### the nature of the electromagnetic induction

the electromagnetic induction: is it a magnetic force (Lorentz Force) or an electric force generated by the temporal variation of the magnetic field (Faraday's law)?
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### Generating electricity from a magnet rotating around the Earth at its orbital velocity?

As the title implies, can we induce electricity from a semi-perpetual moving magnet by gravity(at its orbital velocity? I know there is no perpetual motion, but the magnet can fly for years without ...
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### Two metal balls in a capacitor

The situation is: let's have a capacitor connected to a voltage souce (I guess it's safe to assume that the capacitor is very long, so we don't have to consider effects at its edges). And in this ...
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### Transforming absolute temperature into electricity via ions?

I had a thought experiment. Suppose you fill a conducting metal box with ions or other charged particles. Accelerating charges generate electromagnetic field, which induces a current in the ...
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### If you are vacuuming your carpet and you wrap the cord around your body do you become a magnet?

If you wrap an active electric cord around your body, do you become an electromagnet?
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### how is motional EMF developed?

According to my textbook and several other sources on the internet if we we move a rod in the direction perpendicular to a uniform magnetic field, the electrons will also move as per the direction ...
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### What are current density in these experiments with neodymium magnet levitation?

Here is the video: https://www.youtube.com/watch?v=keMpUaoA3Tg Experimenter throws neodymium magnet into copper tube. Apparently, it induces currents in the copper, which create magnetic fields, ...
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### Electrostatic Induction and Flow of Charges

I have a couple of questions which come under the above title. 1) Firstly if we bring a negatively charged rod near a sphere (Fig 1 and 2) The end A would get positively charged and the end B ...
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### Whats the Induced EMF in this case?

I have taken a very long solenoid, lets suppose it of radius r, the magnetic field changes at the rate dB/dt ,now if i tried to calculate the induced emf for the triangular circuit ABC, i need to find ...
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### Does terminal voltage decrease as we draw current?

If the secondary is an open circuit or the current taken from it is small, then to a good approximation $ε_s = v_s$ where $ε_s$ and $v_s$ are secondary voltage(induced) and secondary terminal ...
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### Conductor in motion in a magnetic field

I have the following exercise: there is a square conductor of a given side L and resistance R. The conductor is surrounded by a magnetic field B (90° with the y-axis) and it depends from z: B(z) = K*z,...
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### Spinning a bar magnet above a disc

I'm preparing for a physics exam and this scenario was in one of the past papers: If I have a horizontal bar magnet connected to a motor, and directly underneath there is a horizontal copper disc ...
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### Why does induced current depend on the area of a loop of wire?

My year 12 physics textbook teaches the concept of electromagnetic induction in a rather unintuitive way. Perhaps it is not being thorough. Perhaps I am not being thorough in reading it. Here is my ...
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### Use of tungsten as an insulator in an induction heater

One problem in induction heating is that energy is lost because the object being heated radiates energy, that energy then heats the coils (which are water cooled) and the coils suck away the energy. ...
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### What is the method to find field at the center of a conducting shell due to induced charges due to an outside charge? [closed]

For example, if we had to find the field at Q1 due to the induced charges on the outside spherical surface ,what should be our approach? According to me, as the induced charges due to q2 on the ...
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### How did physicists know that only negative charges move?

I have phrased similarly another question about how physicists knew that two charges exist, positive and negative. The purpose of the question is not necessarily to educate me historically. It's just ...
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### Measurement of electrostatic induction

How is it with the electrostatic induction measurement? Everywhere you can read about the effect of electrostatic induction but I still can't found any detailed explanations or quantitative ...
5k views

### Do induction chargers waste electricity?

Do induction chargers use more energy than traditional chargers while plugged in to the mains but not charging a device?
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### Behavior of coil and resistance in DC circuit [closed]

I have a simple circuit of a coil parallel to a resistance and then in series with another resistance. I wanted to understand the behavior of this circuit so I ran a simulation, and what I noticed is ...
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### How to calculate the energy transfer between working coil and working piece and dissipated energy of working piece in induction heating?

For who don't know how does induction heating work, a short description can be found here. However, my question is about physics. Assume I have a coil inductor calculated carefully 50 uH as below: ...
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### What would happen if a magnet was pushed towards a copper tube in space?

So the question was inspired by one of curious comments on youtube. What exactly would happen if you pushed a strong neodymium magnet towards the copper tube (aiming for the opening in an effort to ...
573 views

### Potential difference between 2 points in a wire carrying induced current

I came across this problem in my physics book. It states that if we were to have a wire AB moving perpendicularly upwards to a magnetic field going into page, as shown in the figure, which point, A or ...
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### Torque on a charged ring

I have been studying electromagnetic induction. As I understand, a magnetic field will exert a force on a moving charge. What I would like to know is whether a changing magnetic field will exert a ...
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### Inductor potential difference direction

If you have increasing current going down an inductor, the inductor will produce a potential difference to produce a counter current in the opposite direction, or up. The lower potential is then on ...
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### Two Jumping Rings Go Higher than One. Why?

When I do the Thomson's jumping ring demo with one aluminum ring it rises up in the air to some height. When I place two identical rings on top of each other and repeat the demo, both rings rise ...
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### If a purely inductive circuit is started in presence of gravity, will the power source ever run out? [closed]

I have read that purely inductive circuits do no work. So if an Inductor with an AC source, coming from an inverter is set up, will the source of power ever run out due to work against gravity? This ...
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### How much current travels transversely in a coil ?

Excuse the the cryptic q. I was just wondering, say in a guitar pickup or AC transformer, we have a coil of copper wire that is coiled around a magnetic core(s). Current is induced in the wire by the ...
533 views

### Inductive loop: Rectangular vs circle shape

In the traffic field there are inductive loops that are installed under the road to detect cars. We cut asphalt and install 3-4 loop of wires like the following picture. The corners are cut ...
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### How is it possible to even develop any current in an inductor?

Potential difference across an inductor (ie p.d. between current exit point and current entry point) is given as $$V= -L\frac{di}{dt} -iR,$$ where $L$ is the inductance of inductor and $R$ is its ...
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### Current induction on a volumic body

The Faraday's induction law states that the temporal variation of the magnetic flux induces an electromotive force, according to the following expression: $$\varepsilon^i=-\frac{d\theta^m}{dt}$$ I ...
635 views

### How do inductors store energy?

I know that in capacitors, when we create a potential difference between the two plates, and then cut off the current, the electrons stay there and this energy is stored. But what is the similar ...
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If motional emf and induced emf are the same, how to explain the emf induced in a conducting rod moving with a velocity perpendicular to length of rod and magnetic field(magnetic field is ...
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### What causes the induced EMF?

I read many different explanation but none of them is satisfying. There is two cases: 1. I move an iron rod in a magnetic field, between two bar magnet for example. To this case I read that when I ...
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### Electromagnetic Induction, specifically induced voltage

Why is it that if a conductor 'cuts through' (what does this mean?) a magnetic field that a potential difference is produced? I read this recently in a textbook...
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### I need proof for dW=eIdt [closed]

I need help to understand from where this equation is formed inorder to continue to study energy stored in an inductor.
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### Efficiency of resonant inductive coupling as a function of distance

What is the relationship between the efficiency of energy transfer between resonant inductive coupling between two coils, and the distance between the coils?
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### Magnetic Forces and Junkyard Magnets: What's Going On? [duplicate]

In my electromagnetic theory class, I learned that magnetic forces do no work. This is easy to see when observing a cyclotron; the speed never changes, so the kinetic energy never changes and ...
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### Kirchoff's rules and inductance

Can Kirchoff's loop rule be applied in a scenario involving an inductor? Kirchoff's loop rule states that the closed loop integral of E dot dl is equal to zero. But, in a situation with an inductor, a ...
446 views

### Point charge inside a electrically neutral cavity in conductor placed eccentrically, and effect of external electric field if switched on

bear with me, but i would like a definite answer, now, starting off the external charge density on the outer surface of sphere WILL be uniform by unique solution of Laplace equation and letting the ...
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### Motion in a time-dependent uniform magnetic field

Suppose you have an infinite solenoid generating an uniform magnetic field inside. The field is oriented along the solenoid axis : unit vector $\vec{\bf n}$. The field intensity varies linearly with ...
I've learnt in high school that in an ideal transformer, $$\frac{V_s}{N_s} = \frac{V_p}{N_p}$$ I looked for derivation for this formula, and in every source I look, the argument goes thus: |V_p| = ...