The number density of electron in copper is `8.5 xx10^(28)m^(-3)`. Find the current flowing through a copper wire of length 20 cm, area of cross section 1 mm square,when connected to a battery of 3 V. Given the electron mobility `=4.5xx10^(-6)m^(2)V^(-1) s^(-1)` and electron charge `=1.6 xx 10^(-19)C`.

The number density of electron in copper is `8.5 xx10^(28)m^(-3)`. Fin

1.	The number density of electron in copper is `8.5 xx10^(28)m^(-3)`. Find the current flowing through a copper wire of length 20 cm, area of cross section 1 mm square,when connected to a battery of 3 V. Given the electron mobility `=4.5xx10^(-6)m^(2)V^(-1) s^(-1)` and electron charge `=1.6 xx 10^(-19)C`.
Answer» Here, `m=8.5 xx 10^(28) m^(-3), I=?` `l=20 cm =0.20 m`, `A=1 mm "square" =10^(-3) xx 10^(-3) m^(2) =10^(-6) m^(2)`, `V=3V, mu =4.5xx10^(-6) m^(2) V^(-1) s^(-1)`, `e=1.6xx10^(-19) C`. Electric field set up in a copper wire `E=V/l =3/0.20 =15 Vm^(-1)` Current, `I=n A e mu E=(8.5 xx10^(28))xx10^(-6)` `xx (1.6 xx 10^(-19)) xx(4.5xx10^(-6))xx5 `=0.918 A`

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