A `1 mu A` beam of protons with a cross - sectional area of `0.5 sq.mm` is moving with a velocity of `3 xx 10^(4) ms^(-1)` . Then charge density of beam is

Options

A. `6.6 xx10^(-4)C //m^3`
B. `6.6 xx10^(-5)C //m^3`
C. `6.6 xx10^(-6)C //m^3`
D. None of these

Answer

B

Explanation

Charge density `= ("Charge")/("Volume")`
`= (ixxt)/("Area" xx"Distance") = ` for unit time Velocity = Distance
`= (10^(-6))/(3xx10^4xx0.5 xx10^(-6))=6.6 xx10^(-5)C//m^3`