# how much current to cancel earth's magnetic field?

It can be shown the magnetic field in a long narrow tube is uniform and given by B(Tesla =1.26E-6 N I(amp)?

where N is number of wire loops/meter. Assuming the solenoid is aligned along the Earth's magnetic field,how much current is needed to cancel the Earth's field?
earth's magnetic field is 10^-4 Tesla

 ebaines Posts: 10,053, Reputation: 5539 Expert #2 Jul 9, 2012, 04:36 AM
Given the equation $B = 1.26 \times 10^{-6} N I$, and given that the earth's magnetic field is $B = 10^{-4}$, set these equal to each other and solve for the current, I.

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