A Beam of Electrons Moves at Velocity

question 55

Multiple Choice

A beam of electrons moves at velocity
) The number of particles per unit volume in the beam of area A is ρ.If we imagine a cylindrical Gaussian surface of radius r and length
Centered on the beam,the electron flux through the surface is

• A)0.
• B)ρv_fA.
• C)2ρv_fA.
• D)ρv_f(A+2πr ).
• E)2ρv_f(A+πr ).

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