Is electric current only a flow of charge?

AI Thread Summary
The discussion centers on the nature of bound currents in magnetized materials, questioning whether they are real or merely a conceptual model. It argues that connecting a galvanometer to a magnetized iron sphere should not yield any deflection, as there is no actual flow of charge along the surface. The concept of surface current is explained as a result of tiny current-carrying loops, but the presence of point particles (electrons) complicates this explanation. Participants agree that the galvanometer cannot serve as a definitive test for the reality of surface currents, as it does not measure the bound current effectively. Ultimately, the conversation suggests that the question of whether bound currents are "real" may not have a meaningful scientific basis.
shubham agn
Messages
20
Reaction score
0
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?
 
Physics news on Phys.org
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?
 

Thread 'Maxwell stress tensor'

This is from Griffiths' Electrodynamics, 3rd edition, page 352. I am trying to calculate the divergence of the Maxwell stress tensor. The tensor is given as ##T_{ij} =\epsilon_0 (E_iE_j-\frac 1 2 \delta_{ij} E^2)+\frac 1 {\mu_0}(B_iB_j-\frac 1 2 \delta_{ij} B^2)##. To make things easier, I just want to focus on the part with the electrical field, i.e. I want to find the divergence of ##E_{ij}=E_iE_j-\frac 1 2 \delta_{ij}E^2##. In matrix form, this tensor should look like this...
View full post »
Thread 'Applying the Gauss (1835) formula for force between 2 parallel DC currents'

Thread 'Applying the Gauss (1835) formula for force between 2 parallel DC currents'

Please can anyone either:- (1) point me to a derivation of the perpendicular force (Fy) between two very long parallel wires carrying steady currents utilising the formula of Gauss for the force F along the line r between 2 charges? Or alternatively (2) point out where I have gone wrong in my method? I am having problems with calculating the direction and magnitude of the force as expected from modern (Biot-Savart-Maxwell-Lorentz) formula. Here is my method and results so far:- This...
View full post »

Similar threads

I Charge movement relative to magnetic field frame dependence/invariance
Replies
5
Views
918
I Capacitor surface charge movement current, relativistic effects
Replies
2
Views
1K
Arbitrariness of the surface involved in the displacement current
Replies
2
Views
1K
I Question on Hall Effect and magnetic force
Replies
2
Views
2K
I How is Potential Difference Created across a Resistor?
Replies
21
Views
4K
I Is the Poynting Vector Field the Only Factor in Energy Flow in Circuits?
Replies
16
Views
3K
A Voltage and current waves in a transmission line
Replies
4
Views
3K
I Can current flow in an open circuit?
Replies
4
Views
3K
I Does a Railgun's Current Violate Conservation of Momentum?
2
Replies
61
Views
5K
B Some Questions about Electric Current/Capacitors to help my understanding
Replies
7
Views
2K

Hot Threads

Recent Insights

Back
Top