Rotating Disk in Magnetic Field

In summary, the conversation discusses the difficulty of understanding how to write the circuit equation inside a rotating disk made of conductor material, with a resistance of r. The equation provided is ir=emf+v(a)-v(b). The direction of the Lorentz force can determine the location of positive charges and the equation reveals the voltage between points A and B. The Lorentz field is always in the radial direction out of the disk, indicating that the positive charge is on point B. Ohm's law is also mentioned as a way to understand the relationship between voltage, current, and resistance.
  • #1
NewEinstein
2
0
Hi I am having a difficulty understanding how to write the circuit equation inside a disk which rotates in magnetic field.
the disk is made of conductor material.
the resistance of the disk is: r
the answer is: ir=emf+v(a)-v(b)
if someone could explain it would be great!
and how do i know where is the positive charge and negative charge
thanks!
upload_2015-9-5_14-37-57.png
 
Last edited:
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  • #2
You can tell where the positive charges are by the direction of the Lorentz force that any charge has, with the direction of every charge's instantaneous velocity is clear.
The equation just unveils the voltage between A and B?
 
  • #3
tommyxu3 said:
You can tell where the positive charges are by the direction of the Lorentz force that any charge has, with the direction of every charge's instantaneous velocity is clear.
The equation just unveils the voltage between A and B?
oh thank you now i got it the lorentz field is always in the radial direction out of the disk so the positive charge is on b..
and yes that is the voltage between A and B but i also got it now from Ohm`s law
 

1. How does a rotating disk in a magnetic field work?

The rotating disk in a magnetic field is based on the principle of electromagnetic induction. When a conductor, such as the disk, moves through a magnetic field, it experiences a force called the Lorentz force. This force causes the electrons in the disk to move, creating an electric current. The direction of the current is perpendicular to both the magnetic field and the direction of motion, causing the disk to rotate.

2. What factors affect the rotation speed of a disk in a magnetic field?

The rotation speed of a disk in a magnetic field is affected by several factors, including the strength of the magnetic field, the speed at which the disk is moving, and the angle between the magnetic field and the direction of motion. Additionally, the material and size of the disk can also impact the rotation speed.

3. What is the purpose of a rotating disk in a magnetic field?

A rotating disk in a magnetic field has various practical applications. It can be used to generate electricity in devices such as generators and alternators. It can also be used in sensors to measure the strength and direction of a magnetic field. Additionally, it is used in some motors and turbines to convert electrical energy into mechanical energy.

4. How is the direction of rotation determined in a rotating disk in a magnetic field?

The direction of rotation in a rotating disk in a magnetic field is determined by the right-hand rule. If the thumb of your right hand points in the direction of motion, and your fingers curl in the direction of the magnetic field, the direction of rotation will be perpendicular to both, in the direction of your palm.

5. Can a rotating disk in a magnetic field produce a constant rotation speed?

No, the rotation speed of a disk in a magnetic field is not constant. It depends on the factors mentioned in question 2, which can vary. However, the rotation speed can be controlled by adjusting these factors, such as changing the strength of the magnetic field or the speed at which the disk is moving.

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