An electron having a kinetic energy of 100eV circulates in a path of radius 10cm in a magnetic field. Find the magnetic field and the number of revolutons per second made by the electron.

Explanation

`KE = 100 eV = 1.6 xx 10^(-17)J `
` (1)/(2) xx 9.1 xx 10^(-31) xx V^(2) = 1.6 xx 10^(-17) J`
` rArr V^(2) = 0.35 xx 10^(14)`
` or , V = 0.591 xx 10 ^(7) m/s `
` Now r= (mV) / (qB) rArr B = (mV)/ (qr) `
` B = 3. 3613 xx 10^(-4) T `
` = 3.4 xx 10 ^(-4) T`
No f cycles per second
` = (1)/(T) = 0.0951 xx 10 ^(6)`
` = 9.51 xx 10^( 6)`
Potting ` B = 3.361 xx 10 ^(-4) T `
We get f = 9.6 xx 10^(6) `