Question

A current of 1.0 A is flowing through a copper wire of length 0.1 m and corss-section 1.0 X 10⁻⁶ m².
(i) If the resistivity of copper be 1.7 x 10⁻⁸ Ω m, calculate the potential difference across the ends of a wire.
(ii) Determine the drift velocity of electrons.
[Density of copper = 8.9 x 10³ kg m⁻³, valancy of Cu = 1, atomic weight of copper = 63.5 g mol⁻¹, NA = 6.02 x 10²³ mo1⁻¹]

Answer 1

Dear Student,

◆ Answer -

(i) Potential difference = 1.7×10^-3 V

(ii) Drift velocity = 7.4×10^-5 m/s

◆ Explaination -

(i) Potential difference across wire is -

V = IR

V = Iρl/A

V = 1 × 1.7×10^-8 × 0.1 / 10^-6

V = 1.7×10^-3 V

(ii) No of electrons per cu.m. is -

n = valence × NA × d / M

n = 1 × 6.022×10^23 × 8.9×10^3 / 63.5×10^-3

n = 8.44×10^28 /m^3

Drift velocity of electrons is given by -

v = I/(nAe)

v = 1 / (8.44×10^28 × 10^-6 × 1.6×10^-19)

v = 7.4×10^-5 m/s

Hope this helps you...