You wish to make a mass spectrometer with a chamber 57 cm on

You wish to make a mass spectrometer with a chamber 57 cm on a side.

Part A

How large a magnetic field is needed to keep singly ionized helium atoms (4He) with kinetic energy 300 eV within the chamber?

Express your answer to two significant figures and include the appropriate units.

D=57cm

r=D/2 =28.5 cm

mass of helium ,m=6.692*10^-27 kg

KE=(1/2)mV^2

=>V=sqrt(2KE/m)

V=sqrt(2*300*1.6*10^-19/6.69*10^-27)

V=119.79*10^3 m/s

magnetic field is given bt

B=mV/qr =(6.69*10^-27)(119.79*10^3)/(1.6*10^-19)*0.285

B=0.01757 T or 17.57mT