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 xx 10^(-4) C//m^(3)`
B. `6.6 xx 10^(-5) C//m^(3)`
C. `6.6 xx 10^(-6) C//m^(3)`
D. None of these

Answer

B

Explanation

For one second , distance = velocity = `3 xx 10^(4) m//sec` and `Q = i xx 1 = 10^(-6) C`.
`"Charge density" = (" charge )/(Volume")`
` = (10^(-6))/( 3 xx 10^(4) xx 0.5 xx 10^(-6))`
`= 6.6 xx 10^(-5) C//m^(3)`.