A long coil with a thread density of 5 threads per centimeter is turned so that its axis is oriented in the north-south direction. We pass a current through the coil in such a direction that it opposes the Earth's magnetic field and we notice that at a current of 0.044 A, the magnetic field density inside the coil drops to zero. Calculate the horizontal component of the Earth's magnetic field density. What magnetic field density would be measured if the current were passed through the coil in the opposite direction? The permeability of free space is 
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