# physics

posted by .

What magnetic field is required to constrain an electron with a kinetic energy of 400eV to a circular path of radius .80m? (answer: 8.4x10^-5T) What equation(s) do I use? Any help is appreciated!

• physics -

V = sqrt (2E/m) relates velocity to energy.

E = 400 eV *1.6*10-19 J/eV = 6.4*10^-17 J

e V B = m V^2/R
That equates the magnetic force to the centripetal force

B = m V/(R e) = [sqrt(2 E m)]/(R e)

## Similar Questions

1. ### physics

An electron of kinetic energy 41 keV moves in a circular orbit perpendicular to a magnetic field of 0.330 T. (a) Compute the radius of the orbit. The answer to this part is 2.07mm. (b) Find the frequency of the motion. I'm not sure …
2. ### physics

An electron has a kinetic energy of 4.2 x 10-17 J. It moves on a circular path that is perpendicular to a uniform magnetic field of magnitude 3.3 x 10-5 T. Determine the radius of the path. The electron in the problem has Charge of …
3. ### physics

A proton with a kinetic energy of 5.00E-16 J moves perpendicular to a magnetic field of 0.289 T. What is the radius of its circular path?
4. ### Physics

A proton and an electron have the same kinetic energy upon entering a region of constant magnetic field. What is the ratio of the radii of their circular path?
5. ### Physics

A proton and an electron have the same kinetic energy upon entering a region of constant magnetic field. What is the ratio of the radii of their circular path?
6. ### physics numerical

an electron moving with the speed of 1067 m/s is passed into a magnetic field of intensity 0.1T normally.what is the radius of the path of the electron inside the field?
7. ### Physics

An electron moves on a circular orbit in a uniform magnetic field. The strength of the field is 1.00×10-5 tesla. The kinetic energy of the electron is 178.0 eV. (1 eV = 1 electron volt = 1.6 ×10−19 joules.) Calculate the radius …
8. ### Physics

An electron has a kinetic energy of 7.00 10-17 J. It moves on a circular path that is perpendicular to a uniform magnetic field of magnitude 4.40 10-5 T. Determine the radius of the path?
9. ### physics

explai biot-savart,law.an electron with velocity 3*107ms1 describe a circular path in a uniform magnetic field of 0.2T,perpendicular to it.calculate the radius of path
10. ### physics

an electron with velocity v=3x10 to the power 7 m/s describes a circular path in a uniform magnetic field of 0.2T perpendicular to it calculate the radius of the path?

More Similar Questions