Magnetic Force on Electron: Unanswered Mystery

[dcgirl16]

an electron moves within a uniform magnetic field of .2T at a speed of 5x10^5 m/s. What is the magnetic force on the electron?

I used Fm=qvBSin and got 1.6x10^-14N but the answer is that it can't be determined with this info why not?

 

[nrqed]

an electron moves within a uniform magnetic field of .2T at a speed of 5x10^5 m/s. What is the magnetic force on the electron?

I used Fm=qvBSin and got 1.6x10^-14N but the answer is that it can't be determined with this info why not?

Because you don't know the angle between the velocity of the electron and the magnetic field! You are right that the magnitude of the magnetic field is $F_m = |q| v B sin \theta$ but without the angle $\theta$ you can't find the answer. (how did {\em you} get an answer? I bet that you used an angle equal to 90 degrees!)

Patrick

 

[kyle8921]

There are a few reasons why the magnetic force on the electron cannot be accurately determined with the given information.

Firstly, the equation Fm=qvBSin only applies to a charged particle moving in a magnetic field if the velocity of the particle is perpendicular to the magnetic field. In this case, it is not specified whether the electron's velocity is perpendicular to the magnetic field of 0.2T. If the electron's velocity is not perpendicular, the force calculation would be incorrect.

Additionally, the equation assumes that the electron's path is a perfect circle, which may not be the case in reality. The actual path of the electron may be slightly curved or even spiral due to other forces acting on it, which would also affect the calculation of the magnetic force.

Furthermore, the given information does not specify the charge of the electron, which is necessary for calculating the force. Since the charge of an electron is very small (1.6x10^-19 Coulombs), even a slight difference in the charge would result in a significantly different force calculation.

Lastly, the given information only provides the magnitude of the velocity and magnetic field, but not the direction. The direction of the velocity and magnetic field relative to each other also affects the force calculation.

In conclusion, the magnetic force on the electron cannot be accurately determined with the given information due to the lack of specific details and assumptions made in the equation. Further information, such as the direction of the velocity and magnetic field, the charge of the electron, and the actual path of the electron, would be necessary for a more precise calculation.