Plastic disc with a coil wound around is axis of rotation

In summary, the question is whether the disc, with a coil of wire around its axis of rotation and a net charge at its circumference, will rotate when the current in the coil is instantaneously brought to 0. The collapse of the dipole magnetic field creates a concentric electric field which induces a force on the charges and makes them rotate. However, by the law of conservation of momentum, the disc should not rotate. The question remains whether the disc will rotate or not.
  • #1
sridhar_n
85
0
A question,

I have a plastic disc with a coil wound around is axis of rotation. The coil carries current I. Now the disc carries charges at its circumference. Now the current flowing in the coil is brought to 0 instantaneously. This creates Electric Field to be produced that travel in concentric circles and induce a force on the charges and make them rotate. However, by law of conservation of momentum, the disc must not rotate. The question is, will the disc rotate or not?

Happy Solving...

Sridhar
 
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  • #2
Just to clarify:

I'm picturing something like a pencil with a coil of wire around it, this is the axis of rotation? And a thin, non-conducting disk that has a net charge at its outer edge?

And by shutting off the current, the collapse of the dipole magnetic field creates an electric field that is concentric with the disk. Is my image correct?

When the force is exerted on the charged rim of the disk, the charges begin to move. These moving charges create their own magnetic field which in turn exerts a force on the charges in the coil. If the coil was free to move, it would rotate in the opposite direction from the disk. If the coil was held in place then the entire world would share in the angular momentum and the effect would not be noticed.
 
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1. What is the purpose of a plastic disc with a coil wound around its axis of rotation?

A plastic disc with a coil wound around its axis of rotation is commonly known as an electric motor. Its purpose is to convert electrical energy into mechanical energy, allowing the disc to rotate.

2. How does a plastic disc with a coil wound around its axis of rotation work?

The coil, also known as an armature, is placed between two magnets with opposite poles facing each other. When an electrical current is passed through the coil, it creates an electromagnetic field that interacts with the magnetic field of the magnets, causing the disc to rotate.

3. What materials are commonly used to make a plastic disc with a coil wound around its axis of rotation?

The plastic disc is typically made of a lightweight and durable material such as plastic or aluminum. The coil is made of copper wire, and the magnets are usually made of a combination of iron, nickel, and cobalt.

4. What are the advantages of using a plastic disc with a coil wound around its axis of rotation?

One of the main advantages is its compact and lightweight design, making it suitable for various applications such as household appliances, toys, and industrial machinery. It also has high efficiency and low maintenance requirements.

5. What are some common uses of a plastic disc with a coil wound around its axis of rotation?

Electric motors are used in a wide range of devices, including fans, pumps, drills, and electric vehicles. They are also commonly used in manufacturing processes, such as conveyor belts and assembly line machines.

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