Example 3 1 a Estimate the average drift speed of conduction

Last updated: 6/25/2023

Example 3 1 a Estimate the average drift speed of conduction electrons in a copper wire of cross sectional area 1 0 x 107 m carrying a current of 1 5 A Assume that each copper atom contributes roughly one conduction electron The density of copper is 9 0 x 10 kg m and its atomic mass is 63 5 u b Compare the drift speed ob Ined above with 1 thermal speeds of copper atoms at or inary temperatures ii speed of propagation of electric field along the conductor which causes the drift motion Solution a The direction of drift velocity of conduction electrons is opposite to the electric field direction i e electrons drift in the direction of increasing potential The drift speed v is given by Eq 3 18 V I neA Va Now e 1 6 x 10 19 C A 1 0 x 107m I 1 5 A The density of conduction electrons n is equal to the number of atoms per cubic metre assuming one conduction electron per Cu atom as is reasonable from its valence electron count of one A cubic metre of copper has a mass of 9 0 x 10 kg Since 6 0 x 1023 copper atoms have a mass of 63 5 g 6 0 x 1023 63 5 8 5 x 1028 m n which gives V x9 0 106 1 5 85x1028 x 16 x 10 19 V 010 7