Calculating Maximum Magnetic Force on an Electron in a Television Set

[buckeyes]

In a television set, electrons are accelerated from rest through a potential difference of 23 kV. The electrons then pass through a 0.28 T magnetic field that deflects them to the appropriate spot on the screen. Find the magnitude of the maximum magnetic force that an electron can experience.

i know to use F=qvB to find max but i am having trouble getting the right units to find v i use (1/2)mv(sq.). but how do i get 23kV in the right units to use this equation?

 

[Dick]

An electron passing through a potential difference of V volts gains an energy of q*V where q is the electron charge. So that's it's kinetic energy KE=(1/2)mv^2 (where v here is velocity). Equate the two energies and find the velocity.

 

[buckeyes]

do i use 23kV or do i need to convert that unit?

 

[Dick]

23kV=23000V. Just multiply that by the charge in (in coulombs) of an electron. Volts are measured in joules per coulomb. See? The units will come out just right.