If n, e, `tau`, m, are representing electron density charge, relaxation time and mass of an electron respectively then the resistance of wire of length 1 and cross sectional area A is given by

Options

A. `(ml)/("ne"^(2)tauA)`
B. `(m tauA)/("ne"^(2)l)`
C. `("ne"^(2)tauA)/(ml)`
D. `("ne"^(2)ml)/(tauA)`

Answer

A

Explanation

`R=rho 1/A`
Since we know resistivity is given by
`rho=m/("ne"^(2)r)`
Resistance `R=(ml)/("ne"^(2)tauA)`
where
m=Mass of electron
l= length of conductor
n=charge density
e=charge of electron
`tau`= relaxation time
A=cross sectional area