How Do Electric and Magnetic Fields Behave Around a Moving Electron?

[gstrosx]

Homework Statement

An electron is moving with a speed of 3*10^6 m/s. What are the directions (NE, N, NW,..., In the screen, out of the screen, zero magnitude) of the electric and magnetic field. What is the magnitude of the electric and magnetic field?

     moves this direction 3e6
     /
    / angle = 60 degrees
electron-------------------------Observation location, d = 3e-10

Homework Equations

for field direction the right hand rule is applicable

E=N/C
B=T

The Attempt at a Solution

Efield is similar to a Efield from a electric circuit, applying the right hand rule in the opposite direction of the movement of the electron gives out of the screen.

Mfield is, at a speratic guess (using a left hand rule i think) is East

|E|=1/4pi epsilon naught * chargeOfelectron/d^2

|B|=googly eyes.

 

[foxjwill]

You're confusing the direction of the E-field with that of the B-field. Remember that the E-field due to a point charge is

$$\textbf{E}=\frac{Q}{4\pi \epsilon_0 r^2}\ \hat{\textbf{r}}$$​

and the B-field due to a point charge is

$$\textbf{B} = \frac{\mu_0}{4\pi} \frac{q\textbf{v} \times \hat{\textbf{r}}}{r^2}$$​

 

[Moetasim]

I would like to clarify a few things. First, the right hand rule can be used to determine the direction of the electric and magnetic fields, but it is important to specify which hand and which fingers are being used. In this case, the right hand rule for a positive charge moving in the direction of the thumb would give the direction of the magnetic field. To determine the direction of the electric field, one could use the left hand rule for a negative charge moving in the direction of the thumb.

Secondly, the equations given for the magnitude of the electric and magnetic fields are correct, but it is important to note that the electric field is dependent on the charge of the electron, while the magnetic field is dependent on the speed of the electron. So, the magnitude of the electric field would be much larger than the magnitude of the magnetic field in this scenario.

Finally, without knowing the exact distance between the electron and the observation location, it is not possible to determine the exact magnitude of the electric and magnetic fields. However, it is safe to assume that the magnitude of the electric field would be much larger than the magnitude of the magnetic field, as the distance between the electron and the observation location is very small compared to the speed of the electron.