# Calculating Induced EMF in a Coil with Uniform Magnetic Field

• Sir_Pogo
In summary, the conversation revolves around a homework problem involving a copper wire, a toilet paper roll, and a uniform magnetic field. The goal is to calculate the magnitude of the induced EMF in the wire, given the radius of the roll, strength of the field, and velocity at which the wire is unrolled. The key concept is Faraday's Law, where EMF is equal to the change in magnetic flux over time. The difficulty lies in understanding the relationship between the number of wire turns and time, and the importance of posting homework questions in the appropriate forum.
Sir_Pogo
I have a homework problem where there is a long copper wire around a toilet paper roll that is placed in a uniform magnetic field. The axis of the roll is aligned with the field.
I am given the radius of the roll, strength of the field, and a velocity at which the wire is unrolled.
How do i calculate the magnitude of the EMF induced in the wire??

How do you associate a speed to the unrolling?!? I don't understand.
Could you post the problem exactly as it it written please?

Btw - you posted in the wrong forum. Next time, please post in the appropriate sub-forum among those:

https://www.physicsforums.com/forumdisplay.php?f=152

Note that as it's said in Faraday's Law EMF is equal to d(N*magnetic_flux)/dt where N is a total amount of wire turns and magnetic_flux is per each one.

In your example your, magnetic_flux is const. and equal to BS=pi (r)^2 B. And only N changes in time. Try to think about dependence between N and time

What I have a lot of trouble understanding is... how do people with some sort of science education consistently misinterpret the sticky at the top of the forum that says 'Do not post your homework questions here.'? There are forums for that, but this is not one of them.

## 1. What is "unraveling coil inducing EMF"?

"Unraveling coil inducing EMF" refers to the process of creating an electromagnetic field (EMF) by unraveling a coil of wire. This is achieved by passing an electric current through the wire, which creates a magnetic field around the wire. The strength of the EMF is determined by the number of turns in the coil and the amount of current passing through it.

## 2. How does "unraveling coil inducing EMF" work?

When an electric current flows through a wire, it creates a magnetic field around the wire. The strength of this magnetic field is directly proportional to the amount of current passing through the wire. By unraveling the coil of wire, the magnetic field is spread out and becomes stronger. This creates an electromagnetic field, which can be used for a variety of applications such as powering devices or transmitting information.

## 3. What are the applications of "unraveling coil inducing EMF"?

"Unraveling coil inducing EMF" has a wide range of applications, including powering devices such as motors, generators, and transformers. It is also used in wireless communication systems, such as radio and television broadcasting, where the EMF is used to transmit information through the air. Additionally, it has medical applications, such as in magnetic resonance imaging (MRI) machines, which use strong EMFs to produce detailed images of the body.

## 4. What factors affect the strength of the EMF created by "unraveling coil inducing EMF"?

The strength of the EMF created by "unraveling coil inducing EMF" is affected by several factors, including the number of turns in the coil, the amount of current passing through the wire, and the type of material used for the wire. Additionally, the distance between the wire and the object influenced by the EMF can also impact its strength.

## 5. Are there any safety concerns with "unraveling coil inducing EMF"?

While EMFs created by "unraveling coil inducing EMF" are generally low and considered safe, there are some safety concerns to be aware of. Prolonged exposure to strong EMFs can potentially cause health risks, such as headaches, fatigue, and even long-term damage to cells. It is important to follow safety guidelines and regulations when working with or near strong EMFs, and limit exposure when possible.

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