# Reality of bound currents

• shubham agn
In summary: Electric current is actually the flow of electrons through a material. It does not have to be the flow of charge.

#### shubham agn

A magnetized object is always described as having bound volume and surface current. Are these bound currents real? I mean if I connect a galvanometer between two points on the surface of a magnetized iron sphere, will the galvanometer show a deflection?
If it does then it is very strange because Iron is magnetized because of the spin of its electrons which are point particles. So they can't really create a "flow" of charge along the surface to create a surface current. How then can we explain the "reality" of surface current?

Let's suppose that the current were real. How much deflection would you expect to see on the galvanometer?

DaleSpam said:
Let's suppose that the current were real. How much deflection would you expect to see on the galvanometer?
I think no deflection should be seen as there is no charge that is flowing along the surface. In Griffiths text on Electromagnetism, the author has explained the surface current as being caused due to tiny current carrying loops whose current "touches" the surface. The cumulative effect of all such loops would be a surface current (although it is not due to continuous flow of charge). But in real materials there are no such tiny loops inside but electrons instead of them which are point particles. So now we evidently cannot explain the surface current. So in this case, the surface current is not there apparently and is just an imaginary physical model to describe the magnetization. Am I right here?

No deflection of no galvanometer. You're right.

shubham agn said:
I think no deflection should be seen as there is no charge that is flowing along the surface.
You are correct, no deflection should be seen. A galvanometer measures current through the galvanometer. The bound current is bound to the surface of the magnet, so it doesn't flow through the galvanometer.

My point is, if you want to decide if something is "real" then you have to figure some experiment that would be different if it were real or not. The galvanometer is not such an experiment because regardless of whether it is real or not it doesn't flow through the galvanometer and therefore you don't expect anything different.

I cannot think of any such experiment, so I don't think that the "is it real" question is scientifically meaningful.

Who sais that electric current is only flow if charge?

## 1. What are bound currents?

Bound currents are electric currents that exist within a material, such as a conductor or dielectric, due to the presence of electric charges that are bound to the material's atoms or molecules. These charges do not move freely like in a traditional electric current, but they can still produce magnetic fields and have an impact on the overall behavior of the material.

## 2. How do bound currents differ from free currents?

Bound currents differ from free currents in that they are not caused by the movement of electric charges, but rather by the alignment or rearrangement of charges within a material. Free currents, on the other hand, are caused by the flow of electric charges through a conductor.

## 3. What is the significance of bound currents in electromagnetism?

Bound currents play a crucial role in electromagnetism as they contribute to the overall magnetic field of a material. They are also important in understanding the behavior of materials in various electromagnetic fields, such as in the case of dielectrics or magnetic materials.

## 4. How are bound currents calculated?

Bound currents can be calculated using Maxwell's equations, which describe the relationship between electric and magnetic fields. The equations take into account the displacement current, which is caused by the changing electric field within a material, and the bound current, which is caused by the bound charges within the material.

## 5. What are some real-world applications of bound currents?

Bound currents have numerous real-world applications, such as in the design of electronic components, where the behavior of materials in different electromagnetic fields must be taken into account. They are also used in medical imaging, such as in MRI machines, where the magnetic properties of materials are crucial in producing images of the body's tissues.