An electron in the beam of a cathod-ray tube is accelerated by a potential difference of 2.12 kv . then it passes through a region of transverse magnetic field, where it moves in a circular arc with a radius of 0.170 m .
what is the magnitude of the field?

B=9.1397*10^-4 Tesla

Explanation:

To find the velocity first we put kinetic energy og electron is equal to potential energy of electron

K.E=P.E

where :

m is the mass of electron

v is the velocity

V is the potential difference

   eq 1

Radius of electron moving in magnetic field is given by:

      eq 2

where:

m is the mass of electron

v is the velocity

q=e=charge of electron

B is the magnitude of magnetic field

Put v from eq 1 into eq 2

B=9.1397*10^-4 Tesla

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it