A copper wire of diameter `0.16 cm` connected in series to an aluminum wire of diameter `0.25cm`. A current of `10` ampere is diameter through them Find (a) current density in copper wire (b) drift velocity of electron in the aluminium wire .The number of free electrons per unit volume of aluminium wire is `10^(29)m^(-3)`

Answer

(a) `4.79 xx 10^(6)Am^(-2)`(b) `1.28 xx 10^(-4)ms^(-1)I`

Explanation

Since the two wires are joined in series the current through each wire is the same i.e. `I = 10A`
(a) For copper wire `A = pi D^(2)//4`,
current density `J = I//A = I//(pi D^(2)//4)`
(b) For aluminum wire , `A' = pi D^(2)//4`
`= pi (0.25 xx 10^(-2))^(2)//4`
`= 2.01 xx 10^(-6)m^(2), n = 10^(29)m^(-3)`
Drift velocity, `upsilon_(d) = I//n A'e`