Electromagnetic induction Definition and 240 Threads

Say for you had a wire in a complete circuit inside a magnetic field (pointing inwards) perpendicular to the wire. You move the wire across (to the right) , cutting lines of flux, this induces a current in the wire. The induced current acts upwards using the dynamo rule (thumb is motion...

Homework Statement In science class, we are supposed to explain how a generator works and functions. However, we have to incorporate coulomb's law in our explanation. Homework Equations F=kQ1Q2/r^2<-- coulomb's law The Attempt at a Solution How I understood it was that a generator consists of...

I have been thinking about coils of wire carrying alternatingcurrent. From what I understand, a back emf is induced in the coil because there is a changing magnetic field around each individual loop of wire, and therefore there is a changing flux through each loop because the changing field...

i have heard it said that back force occurs in generators and back emf occurs in motors, however I was considering a motor and I thought that it seems to me that as the coil is rotating and it has the changing flux linkage, and thus a back end is induced in it by Lenz's law, this reduces the...

Homework Statement (See image) a closed circular wire A lies in the plane of the wire B in the circuit. Deduce the direction. Of the induced current in A when (A) the switch is closed (B) the switch is opened (C) the wire A is raised out of the plane of the paper. Homework EquationsThe...

I have two wires in parallel at a distance r apart. They are unequal in length. The current carrying primary generates a magnetic field B at distance r. What is the area related to the secondary through which B passes? Is it correct to assume the thickness times the length of the secondary? All...

Hey, guys, I encountered this and confused about it. "In a perfect conductor, an arbitrarily large current can be induced, and the resulting magnetic field exactly cancels the applied field." But I suppose, according to Faraday's law,the magnitude of emf is the rate of change of magnetic flux...

Matter can neither be created nor destroyed...but potential energy can be converted into a different kind of energy. Let's say we have a spring with a mass connected to it. This mass is a magnet, and the apparatus is inside a copper coil. It's a horizontal magnet with friction minimized at the...

The magnetic field that is oriented perpendicularly through a 9.2 cm diameter coil of wire drops from 6.4 T to 6.1 T in 0.076 seconds. What is the emf induced in the coil? Trying to answer this. My question is, if they are perpendicular then does that mean that cos90 makes phi = BAcos theta...

Hi guys I just want to know why changing magnetic flux in a coil induces emf? Thanks in advance.

I was just thinking about the "changing magnetic field through a loop induces an EMF" and thought of a conceptual question I'm having trouble with. So, imagine you have an open surface where there's a changing magnetic flux that you know (say its a plane of magnetic field coming toward you...

$\newcommand{\uvec}[1]{\boldsymbol{\hat{\textbf{#1}}}}$ There is a uniform magnetic field $\mathbf{B}$ directed along the axis, and confined to a cylindrical volume of radius $R$. The magnitude of $\mathbf{B}$ is decreasing at a constant rate of $10$ mT/s. In unit-vector notation, what is the...

Homework Statement Homework Equations That is my solution: The Attempt at a Solution i solve my problem without ø=30°, I confused what this angle was used to do?

Homework Statement Thin conducting disc, radius a, thickness b and resistivity p (assumed to be large enough induced currents produce no magnetic field). There is a uniform B field B0sin(wt) parallel to its axis. I first had to find the electric field a distance r from the disc axis in the...

Homework Statement the ans is C for this question. i really have no idea , van someone explain please? Homework Equations The Attempt at a Solution

Homework Statement for this question, i only know that E=-L dI/dt... the ans is C , can anyone explain how to get C? Homework Equations The Attempt at a Solution

Homework Statement A 425 mA conventional current is induced in a 48.0cm wire moved through a magnetic field. A 11.5 Ω resistor is connected to the wire as shown in the diagram below. If the magnetic force acting on the wire is 323 mN, then determine the direction and magnitude of the velocity...

Dear all, I have encountered an issue in understanding how microphone works and I hope you guys can assist. There are two scenarios involved. In the first scenario, there is tuning fork and a microphone. The microphone contains a small disc attached to a magnet and a fixed coil. (Please...

Hello everyone, One very basic thing about this phenomenon is not very clear to me. If a conductor moves in a region of uniform magnetic field, would it have an EMF induced across it? I'm confused because as per Faraday's law, a change in flux through the conductor is necessary for EMF to be...

1. a. coil is moved up and down in the same direction of flux. b. coil is rotated around an axis that is parallel to the flux. c. coil is rotated to the direction of the flux like a dynamo. 2. Electromagnetic inductions laws. 3. I'm really having a hard time...

Homework Statement A circular coil of radius r carries a current I. A magnetic induction B acts at right angles to a diameter of the coil. Show that the current experiences a torque T about the diameter given by T=Iπr^{2}Bsinω, where ω is the angle between the normal to the plane of the coil...

EDIT! Hmmm, sorry. What is the difference between the origin of the emf in a small current loop when; a) a magnet is stationary & the coil moves, b) the coil is stationary & the magnet moves This was the original message, now realized to be incorrect. A current is generated when a...

Hi all, I have a conceptual difficulty with the idea of induction of a current in a wire due to a changing magnetic field. Initially I was very comfortable with the idea. Upon seeing the typical setup of a square wire being rotated in a region of uniform magnetic field, I was happy to accept...

Hello, when a coil rotates in a magnetic field an AC is produced at the ends of the coil but do that electrons come from the coil wire ? If yes, shouldn't the coil run out of electrons after some time ? thank you

Consider a magnet moving towards a coil. We know that the motion of the magnet will induce a current in the coil and the direction of this induced current is to oppose the motion of the magnet. Now does the magnet experience resistance to its motion immediately as soon as it starts...

We know that 1)a change in current and voltage in a coil may result in induction in other stationary coil..this induction is directly related to frequency..ie The higher the frequency the more intense the induction effect. 2)we also know that there is no induction in case of DC current flow...

I first thought that electromagnetic induction disobeyed the law of conservation of energy since there is another current created by another current by changing it (AC). but then there is Lenz law that says when you have yourself an current and also a changing magnetic flux, there will be an...

Homework Statement Here is a question which frequently occurs on on our school test: "Prove Faraday's law of electromagnetic induction on the basis of principle of conservation of energy" I do not really know how to begin.Thanks!

First Post! So I was curious about how I could relate my new found knowledge of electromagnetic inductance on guitar pickups and I came across this on the internet: http://www.sciencebuddies.org/science-fair-projects/project_ideas/Music_p004.shtml#background Which says, "All of these...

A non conducting ring of mass m and radius R has a charge Q uniformly distributed over its circumference. This ring is placed on a rough horizontal surface such that the plane of the ring is parallel to the surface. A vertical magnetic field B=B0t2 τ is switched on. After 2 second from switching...

Homework Statement An iron core with a solenoid coiled around it is in a circuit with a switch and a dc current supply. In front of it, there is a iron ring tied to the ceiling such that it faces the solenoid without touching the circuit. When the switch is turned on what is observed and...

Homework Statement http://imageshack.us/photo/my-images/194/55132039.png/ http://imageshack.us/photo/my-images/194/55132039.png/ How much curret flows trough circuit ABCD when the center of the circuit (O) is distance r from the straight wire? I think these are the relevant equations...

Hi , i am a high school student ( class 10 ) and after reading about electromagnetic induction iwas thinking about what if u place a wire coil connected to a circuit in the magnetic field / near a generator ? Because electricity is turned of for a fraction of a second there will be great...

Hello I am new to this forum and wanted to ask a question on em induction. I know if a current passes through a wire a magnetic field around the wire is produced and can be amplified by having a coil of wire. If that is then placed in a magnetic field (like between a north and south pole...

Apparently for emf to be induced in a coil, the magnetic field (or part of it) has to act along the normal to the coil face. So does this mean that the coil moves side-ways through the magnetic field? where instead of moving through its length (its longer side), it moves through the coil face...

Homework Statement Two metal rods are placed on two parallel smooth conducting rails , under uniform B field lines . The metal rod on right-hand side is initially moving at a constant velocity of 3 m/s , while the other one is initially at rest . What would be the subsequent motions of the two...

Scientifically, it doesn't make sense why you can't just wind up wire without really much air in the middle. In order to get more wire closer to the magnetic flux, why wouldn't you just wind up the coil tighter? I keep seeing ferromagnetic or air cores. Why not a tightly would wire so more...

1. A closed loop is held stationary in the magnetic field between the north and south poles of two permanent magnets held fixed. Can we hope to generate current in the loop by using very strong magnets? well, my doubt is: as magnetic field is a vector and since we have two pairs [one...

Hello everyone, I have the following problem understanding electromagnetic induction. THis is not a homework question but it's a thought experiment I seem to not succeed in doing. Let's take the situation where you move a rectangle shaped plate with a speed perpendicular to a homogenous...

I took a physics competition recently and found I missed 6 questions on electromagnetic induction and the like. I've always been shaky here, so I'm wondering if anyone can give me an online resource, or just explain to me exactly how it works (i.e., Lenz's law, etc., etc.)? I'm sorry for not...

Hello everyone, How are you doing? I have a doubt about electromagnetic induction, in three particular cases. I need to confirm that I have the right concepts, so I ask for your help. The main problem: Imagine that you have a permanent magnet, axially polarized and rotating on its...

Homework Statement If I move a SQUARE conductive layer in a forward direction, with a magnetic field pointing vertically upward why is an EMF only induced in the left-right plane NOT the forward-backward plane??Homework Equations The Attempt at a Solution I would have thought that as BOTH...

Homework Statement You are holding a conducting loop of copper and looking at its circle. Behind it is a long current-carrying wire carrying the current from left to right. As you pull the loop toward you, what is the direction of current flow if any? A)No way to tell B)Counter-clockwise...

When a conducting wire is subjected to a changing magnetic field, what causes the electrons in this wire to move? Conversely, why does the movement of current in the wire (with a non-'moving' magnetic field) cause the wire to move? I understand these phenomena macroscopically (and that they...

I apologize in advance if some of my answers don't quite make sense. I'm generally articulate, but not when it comes to physics I'm barely grasping. I did a lab and part of it was dropping a magnet through a coil, which produced a Voltage vs Time graph using LabPro. For trial 1 we had the N...

Homework Statement A flat coil of wire has an area of 0.010 m2and contains 100 turns. Initially the coil is oriented so that the normal to its surface is parallel to a downward constant magnetic field of 0.2 T. The coil is then rotated clockwise through an angle of 30oin a time of 0.10 s...

Homework Statement An electric generator consists of n = 500 turns of wire formed into a rectangular loop with a length of 5 cm and width of 3 cm placed in a uniform magnetic field of 2.50 T. What is the maximum value of the emf produced when the loop is spun at f = 100 rpm about an axis...

When a magnet is pushed into a solenoid an induced emf occurs. So if it is a closed circuit then an induced current will flow. But if it is an open circuit then an emf will still be induced but no current this time. So will any poles be formed to repel it? What do they mean by the current...

What will happen when I push a magnets into a solenoid with constant speed throughout? I understand that when the magnet leaves and enters an induced emf will occur, but in the middle no emf will occur. Why is this so? I thought that the magnetic flux linkage changes as it moves in the solenoid?

I understand that electromagnetic induction is determined because of a moving electric charge in a magnetic field, but why is the motion necessary? Why is it that motion causes electromagnetic induction and it isn't possible without motion?