At the center of a circular wire of radius 5cm carrying current, magnetic field due to Earth is 0.5×10^-5W/m^2 what should be the current flowing through the wire so it annuls the earth magnetic field?

1 Answer
A08
Jul 30, 2018

With the help of Biot-Savart law it can be shown that magnetic field #bbB# at the center of circular ring of radius #sfr# carrying a current #sfI# is given as

#bbB=sf((mu_0I)/(2r))#
where #sfmu_0# is magnetic permeability of vacuum and #=4pixx10^-7\ sf(Hm^-1)#
#=>sfI=(sf(2r)bbB)/sfmu_0#

Inserting given values in SI units we get

#sfI=(2xx5/100xx0.5×10^-5)/(4pixx10^-7)#
#=>sfI=0.4\ sfA#, to one decimal place.

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