# if an electron is not deflected in passing through a certain space,can we be sure that there is no magnetic feild in that region?

420 Points
13 years ago

Deflection depends on VXB.So if v and b are in same direction then electron will go undeflected even if there is magnetic field(B).

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AKASH GOYAL

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509 Points
13 years ago

no we can not say that there is no magnetic feild....

take a example in which electron is passing through a region where, magnetic field and electric field exist ,both are perpendicular to each other as well as to velocity of particle...

v is the velocity of moving electron then

force due to  electric field is Fe = Eq

Force due to magnetic field is q(vBsin@) or qvB                      (sin90 =1)

if electron is not deflected then total force acting must be zero

qvB=qE

v=E/B....1

that means if there is magnetic field then electron is not deviated but this condition 1 should be fulfilled....