Force of a changing magnetic field

AI Thread Summary
A changing magnetic field induces an electric potential around a loop of wire, causing stationary charges within the loop to experience a force. To determine the direction of this force when charges are not in a loop, Faraday's Law can be applied, leading to the relationship between electric field (E) and magnetic field (B). The Lorentz force equation, F = q(E + |v x B|), simplifies to F = qE for stationary charges, indicating that the force is influenced by the electric field. The direction of the force can vary based on the orientation of the magnetic field and the electric field, potentially aligning with the loop's curvature once the charge begins to move. Isolating E from Faraday's Law involves solving the associated partial differential equation.
DCN
Messages
8
Reaction score
0
By Faraday's Law, we know that a changing magnetic field can induce a potential around a loop of wire and it follows that any charges in the loop will experience a force, otherwise they wouldn't move. Therefore a changing magnetic field exerts a force on stationary charges.

How do you tell the direction of this force is the charge is not in a loop of wire?
 
Physics news on Phys.org
You also use Faraday law, ∇x E = -∂B/∂t, and solve this for E, but remember that the magnetic field is gone yet, so you have lorentz force, F = q(E + |v x B|), however if the charge is stationnary, then just be force it start moving F = qE, F⊥B just because E⊥B (because of the curl), by this you can see that the force can be in any direction even in the direction of the loop if you put the magnetic field in the right angle,once it started moving perpenducular forces are further applied, this you can expect it to be in the direction for the loop (curvature)of the wire
 
How would you isolate E from Faraday's law?
 
DCN said:
How would you isolate E from Faraday's law?
It's a partial differential equation,
 
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...
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...
Back
Top