All Questions

54 questions
40 views

How to calculate induced emf of moving rod?

I have the following exercise: A copper rod with length L is moving on two frictionless conducting rails, in a distance a from an very long straight conductor. The rods resistance: R. Ignore any self ...
65 views

Can $F=qvB$ be applied to a solenoid and a parallel moving magnet?

If you take a scenario like this, Charge gathers at either end, and if you could somehow form a complete circuit without there being a canceling effect, there would be a current flowing. This makes ...
30 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 ...
51 views

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?
83 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 ...
4k views

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?
98 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 ...
69 views

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 ...
64 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 $A$, $I_A$, ...
53 views

When we say flux can't be changed through superconducting coil , because resistance is zero , So this implies there is no induced emf in the coil , If it is so what makes current flow in the coil ...
90 views

Self induced EMF in DC

Why is self induced emf much greater than the source voltage in a DC supply when the switch is opened?
155 views

Inductor in A.C. Circuit

I am reading about inductors connected in A.C. Circuits. I understand mathematically that the current lags behind voltage. But what is the physical explanation for this? My understanding: As the emf ...
66 views

Will a pulsating electron beam passing through a copper pipe induce eddy currents within the copper pipe?

If a pulsating electron beam is beamed down the center of a copper pipe, so as to not make any physical contact with the pipe, the beam should create a pulsating magnetic field that will not change in ...
44 views

Electromagnetic induction and magnetic field (conducting rail problem)

Since we know the work done by a magnetic field is zero.now how does the magnetic field changes the kinetic energy of rod when it applies force BIL (where I is current at any instant) moreover if we ...
214 views

Self Induction and Inductance [closed]

A coil with zero resistance has its ends labeled a and b. The potential at a is higher than at b. Which of the following could be consistent with this situation? Mark all that apply a. The current ...
53 views

Can I induce AC current with a straight piece of wire and a spinning magnet?

The idea is, I have a fast spinning magnet and next to it a wire (with 2 free ends). When the + pole is next to the wire it will attract the electrons, and when the - pole is by the wire it will ...
165 views

Is electromagnetic induction a result of the Hall effect?

I know that an EMF is induced when there's a change in magnetic flux through a conducting surface. Is this due to the Hall effect? By this I mean, do the delocalised electrons in the conductor ...
56 views

Energy conservation in induction

Let's say we have 2 inductively coupled circuits with mutual inductance M, and Circuit 1 ist connected to a power source, changing its current by $\frac{dI_1}{dt}$, then the potential induced in ...
42 views

Effect of greater coils on induced current in a solenoid

Simple case:- A bar magnet is inserted into a solenoid with 'n' turns at velocity 'v'. The current is measured using an ammeter that is part of the complete circuit of the solenoid. My question is ...
146 views

Do magnets attract magnetic materials by inducing magnetism in them?

Here are 2 concise excerpts from a book I have been reading:- 1.A permanent magnet produces its own magnetic field. An induced magnet is a material that becomes a magnet when it is placed in a ...
193 views

Statement of Lenz's law

In Lenz's law we state that direction of the induced current is such that it opposes the cause that produces it. But can we state the direction of induced emf instead of current? If by direction ...
285 views

What does inductance mean?

I have the following notion of inductance. When a current flows through a conductor a magnetic field is set up. Depending on the shape of the conductor we get a magnetic flux through the conductor. ...
666 views

Self Induction: Why does light bulb flash when circuit switched off and not when switched on?

When the switch is closed the current through the coil changes and hence so does the magnetic flux around the coil. This induces an emf in the coil which, in accordance with Lenz's law, will oppose ...
72 views

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 ...
445 views

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 ...
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 ...
57 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 ...
308 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,...
810 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 ...
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 ...
383 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 ...
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 ...
365 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 $B$, ...
127 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 ...
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?
479 views

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 ...
374 views

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 ...
195 views

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 ...
141 views

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 ...
189 views

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 ...
1k views

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 ...
392 views

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, ...
238 views

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 ...
297 views

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 ...
935 views

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: ...
119 views

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 ...
726 views

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 ...
255 views

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.