An 18 gauge copper wire (the size usually used for lamp cords), with a diameter of 1.02 mm,1.02 mm, carries a constant current of 1.67 a1.67 a to a 200 w lamp. the free-electron density in the wire is 8.5×10288.5×1028 per cubic meter. find (a) the current density and (b) the drift speed.

J = 2.044x10⁶ A/m²

v = 1.50x10⁻⁴ m/s

Explanation:  

The current density (J) of the copper wire is giving by:  

where I: electric current and A: cross-sectional area of the copper wire

The cross-sectional area of the copper wire can be calculated by:

Substituting the calculated area in the equation (1) we have:

Hence, the current density is 2.044x10⁶ A/m².    

To find the drift speed (v), we need to use the next equation:

where n: the free-electron density, q: module of the charge of the electron

So, the drift speed is 1.50x10⁻⁴ m/s.

Have a nice day!    

we're given that v₀ = 0 and a = 5.4 m/s². therefore, since v = at + v₀ for constant acceleration the equation for velocity is

after 28s,

m/s

which i would round to 150 m/s as my final answer