At a point high in the Earth\'s atmosphere. He2+ ions in a concentration of 2.5

Question

At a point high in the Earth's atmosphere. He2+ ions in a concentration of 2.5 times 10 power 12/m power 3 are moving due north at a speed of 1.9 times 10 power 6 m/s. Also, a 6.8 times 10 power 11 /m power 3 concentration of is moving due south at a speed of 7.1 times 10 power 6 m/s. Part A Determine the magnitude of the net current passing through unit area (A/m2). Express your answer using two significant figures. Part ? Determine the direction of the net current passing through unit area. North East South West

Explanation / Answer

total charge passing per unit volume due to He2+ ions is

2*(2.5*10^12)*(1.6*10^-19) = 8*10^-7

so current density = J = (charge/unit volume )*speed = 8*10^-7*1.9*10^6 = 1.52 A/m^2

similarly due to O2- ions

J = (6.8*10^11)*(1.6*10^-19)*(7.1*10^6) = 0.77 A/m^2

as the charge on the He2+ ions is positive the current is in the direction of north

and the direction of current is in the north due to O2- ions also becuse current flows in the opposite direction as direction of flow of negative charge

so net current/unit area = 1.52+0.77 = 2.29 A/m^2

PARTB

the direction of the current is north.

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