Questions tagged [induction]

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350 questions
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Induction: How does the electrons in the coil know in which way the magnetic field is moving?

It is well known that a coil will react to a moving external magnetic field in such a way, that the electrons inside it will start moving to produce an internal magnetic field, which counteracts the ...
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How does the emf “know” what the magnetic flux is?

I came across an example in my book where it has the changing flux from a solenoid passing through a larger ring at the end. Here's a picture: How does the large loop (or radius $r_1$) even “know” ...
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Does voltage always cause current?

I'm wondering if the following statement is fully correct: Voltage causes current through a closed circuit, but through an inductor it is the change in current that causes a voltage. Obviously ...
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Can pulsating DC current be transformed?

Since pulsating DC current is changing, why doesn't it induce a changing magnetic flux in the transformer core? Is it able to induce a transformed current in the secondary coil?
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Self induction in a circular coil

There's a formula for self inductance : $$L=\frac{n\Phi}{i}$$ where n is the number of loops. But the book also says self inductance is directly proportional to $n^2$ I totally agree with the ...
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Magnetization of soft iron and steel

I was reading and I saw that the steel becomes permanent magnet whereas iron becomes a temporary magnet after magnetization during magnetic induction. Why does soft iron make temporary magnets and ...
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How to find the direction of an eddy current?

Suppose there is a magnetic field going from left to right. Suppose a thin sheet of metal conductor (e.g. a 1m*1m square) is dropped through the magnetic field such that the plane of the conductor is ...
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Why does AC induction motor rotate the same way?

Suppose an aluminium disc is suspended where it can freely rotate. A magnet is placed above (not touching) the aluminium disc and made to spun. This obvious causes a changing magnetic field. By ...
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How does an inductor store magnetic energy?

I am trying to figure out what the potential energy of an inductor with a current really means. In a capacitor, the energy stored works like this: if you let the plates attract each other, before ...
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Two questions about the nature of induced emf

I have two questions about magnetic induction (I am in university level introductory E and M so maybe my questions will be answered over the next few years): In the linear generator (shown below), I ...
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Can you recommend a/some good book(s) on Faraday for the lay person? In particular, in relation to his 'Experimental Researches in Electricity'. Also, any books explaining how Maxwell explained ...
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Does an Inductor maintain it's energy?

Consider a simple LCR ac circuit; generally I (might) understand that the charge exchange between capacitor and inductor would induce a harmonic current flow, but I remain confused for two reasons: ...
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Does the wireless energy tranmission affect compass

Wireless energy using magnetic inductive coupling. So magnetic field will be affect around device. We use it to charge mobile device so I wonder if it will affect compass in our device
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The image current due to moving charges and a current carrying thin wire

Suppose we have a plane conductor and a stream of positively charged particles of mass m moving parallel to the plane conductor at a distance $d$. The trajectory can be assumed to be straight. An ...
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Uniform field through a disc

Let us say that we have a magnetic field of the form $B_0 \sin(\omega t) \hat e_z$ in all space. Now let us say we put a conducting disc within this field. I want to find the electric field within ...
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Inductance of two parallel wires

I've been asked to calculate the inductance per unit length for two wires or radius $a$ separated by $2d$ where $2d>>a$. Starting from $\int_{s} B.dS = LI$ Im not sure what surface to take? ...
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Why an inductor parallel with a light bulb makes it flash as a key closes the circuit?

The title is a simplified form of my question. To be precise, I'm talking about the following circuit: The inductor has a resistanse equal to the resistor in the circuit. So, the question is that, ...
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Calculating the amount of charges for an object that is electrostatically induced

Induction is one of the ways to get an object electrostatically charged. While positive charges accumulate on one side, negative charges accumulate on the other side for an object in an electric field....
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Induced e.m.f depends on…?

In my revision guide it says that Michael Faraday did experiments that showed that induced e.m.f for a coil of wire depends on four things: Magnetic strength of the core in the coil of wire. (...
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Magnetic Levitation : Confusion with Lenz's Law

Considering the above diagram, I am failing to see why the aluminium ring floats upwards rather than oscillates. I understand Faraday's law, but I am struggling with Lenz's law - as there is an ...
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Electric Field and Neutral Objects

Due to electrostatic induction, when a charged object gets closer to a neutral object, sides of the neutral object can get charged. Thus, a charged object can attract a neutral object. However, is ...
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Voltmeters and changing magnetic fields

A changing magnetic field pierces the interior of a circuit containing three identical resistors. Two voltmeters are connected to the same points, as shown. V1 reads 1 mV. What does V2 read? ...
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Motional emf with rod

We know that $\mathcal{E} = -N \frac{\mathrm{d}\phi}{\mathrm{d}t}$. When we have a rod such as the one on the left moving through a constant magnetic field, how is it the case that the flux is ...
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Shouldn't the currents be time-continuous here?

My intuition is that the current upon an inductor (say, a solenoid) will always be time-continuous, without "sudden changes". But below is a case that seemingly contradicts this point of view. There ...
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How does the voltage across an inductor and a capacitor vary in series LCR circuit about resonance?

I am aware that at resonance, the voltage across the inductor and the capacitor are equal in magnitude and opposite in phase. However, I want to know how the voltage across $L$ and $C$ vary if I vary ...
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Magnetic field and electric field induce one another forever [duplicate]

A changing electric field produces magnetic field and vice versa. Does that mean that this process will carry on forever? Think of a circuit with a capacitor. The magnetic field due to the current at ...
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Induced magnetic field produces electric field and vice versa forever!

So here are the two of Maxwell's laws that I am interested in: So we have the simple circuit (from google): So, before the system goes into steady-state we know that charge slowly accumulates on the ...
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So,i was studying from some lecture notes from MIT's open course program,and i stumbled across this example The example says:The solenoid is so long that its external magnetic field is negligible. ...
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Induced emf problem

This is not homework question,just a thought experiment about a general question i have about induction. Let's suppose that we have a closed circuit with only two resistors in series.We also have a ...
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What happens to the emf generated due to a change in magnetic flux in a coil?

When we move a magnet into a coil of wire (open circuit) and then out of it, we create a emf across the ends of the coil and another emf in the opposite direction. My question is what would happen to ...
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How does an Inductor “store” energy?

It seems to me that an electromagnetic field is nothing more than a collection of photons, which as I've heard, extends through space infinitely. Why is it, then, that an inductor such as simple ...
I've got a basic question on the method of computing the average induction voltage. Here is the task: A conductor loop with the area $A_1 = 50\text{cm}^2$ in a magnetic field with the flux density of ...