# Understanding EMF and Charge Separation in a Changing Magnetic Field

• Icy98
In summary, when there is a changing magnetic flux in a solenoid, an emf is induced. This is due to the circular loops of wire that make up the solenoid. In regards to the questions posed, when there is a separation of charges, there is still an emf present, but the resulting current is zero due to the opposing directions of the emf. As for the attached picture, the direction of the emf may depend on whether the coil is loaded with a resistor or not.
Icy98

## Homework Statement

When there is a changing magnetic flux, emf is induced in the solenoid. The solenoid is made up of circular loops of wire. My first question is, since emd is induced in the solenoid, is there a site of higher voltage and another site of lower voltage? My second question is, (as provided in the picture attached), it is said that at (c), flux does not change hence there is no emf, but there is separation of charges. How is this possible?

## Homework Equations

EMF= -N ( delta phi/ delta time)

## The Attempt at a Solution

For my second question, when there is separation of charges, isn't there an emf?[/B]

#### Attachments

• Screen Shot 2016-06-14 at 6.30.07 am.png
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Icy98 said:
My first question is, since emd is induced in the solenoid, is there a site of higher voltage and another site of lower voltage? My second question is, (as provided in the picture attached), it is said that at (c), flux does not change hence there is no emf, but there is separation of charges. How is this possible?
Have a look at this: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/genwir2.html

So when a winding is moved across the constant magnetic field, an emf will be induced in the right half and the left part of the winding, but the directions of the emf's will be opposite, hence the resulting emf ( the sum of emf's ) in the winding as a whole, will be zero, though there is a voltage difference between the top and bottom of the winding.

And to your attached: Determine whether a current is induced . . . .

Well, we don't know, because we don't know if the coil is loaded by e.g. a resistor, thereby creating a closed current loop.

A magnetic flux induces voltage, Ohm's law must take care of the resulting current ( I = V / R ).

Last edited:
Icy98 said:
For my second question, when there is separation of charges, isn't there an emf?
Think of the left and right-hand sides of the coil as two batteries of identical voltage hooked up + to + and - to -. So there is no current since the two voltages cancel each other.
But the + side is still at a different potential than the - side, by the amount of the battery voltage, right?

## What is electromagnetic induction?

Electromagnetic induction is the process by which an electric current is generated in a conductor when it is exposed to a changing magnetic field.

## How does electromagnetic induction work?

Electromagnetic induction works by Faraday's law, which states that a changing magnetic field will induce an electric current in a conductor. This is due to the movement of electrons within the conductor in response to the changing magnetic field.

## What are the applications of electromagnetic induction?

Electromagnetic induction has a wide range of applications, including generators, transformers, motors, and induction heating. It is also used in devices such as electric guitars, microphones, and wireless charging pads.

## What is the difference between AC and DC in terms of electromagnetic induction?

AC (alternating current) and DC (direct current) refer to the direction of the current flow. In terms of electromagnetic induction, AC is used to describe a changing magnetic field that can induce an alternating current in a conductor, while DC does not have a changing magnetic field and therefore does not induce a current.

## How is electromagnetic induction related to electromagnetism?

Electromagnetic induction is a phenomenon that occurs within the larger concept of electromagnetism. Electromagnetism describes the relationship between electricity and magnetism, and electromagnetic induction is an example of this relationship in action.

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