1.

What is the radius of the path of an electron (mass 9xx10^(-31)kg and charge 1.6xx10^(-19)C) moving at a speed of 3xx10^(7)m//s in a magnetic field of 6xx10^(-4)T perpendicular to it? What is its frequency ? Calculate its energy in keV. (1eV=1.6xx10^(-19)J)

Answer»

Solution :1. When a PARTICLE of mass m and charge q moves in a uniform magnetic field B with speed v radius of its circular path is GIVEN by,
`r=(mvsintheta)/(Bq)`
(where `theta` = angle between `vecvandvecB`)
`thereforer=0.2812m=28.12cm`
2. We have,
`v=romega`
`thereforev=r(2pif)`
`thereforef=v/(2pir)`
= `(3xx10^(7))/((2)(3.14)(0.2812))`
`thereforef=1.699xx10^(7)Hz~~17MHz`
3. Now, kinetic energy of electron is,
`K=1/2mv^(2)`
= `1/2xx9xx10^(-31)xx(3xx10^(7))^(2)`
`thereforeK=4.05xx10^(-16)J`
`thereforeK=(4.05xx10^(-16))/(1.6xx10^(-19))EV`
`thereforeK=2.531xx10^(3)eV`


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