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

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.