As you move further north, the angle of the earth’s magnetic field with respect

Question

As you move further north, the angle of the earth’s magnetic field with respect to the horizontal changes? This angle is referred to as the dip angle.

a) Is this angle below or above the horizontal? Does it increase or decrease as you go further north?

b) Green turtles seem to use this dip angle to determine their latitude. Suppose you are a researcher wanting to test this idea. You have gathered green turtle hatchlings from Islas Marías, Mexico which has a total magnetic field of 41.3T, and dip angle of 48.2°. You then set up a temporary lab on these islands, and put the turtles in a 1.2-mdiameter circular tank and monitor the direction in which they swim as you vary the magnetic field in the tank. You change the magnetic field felt by the turtles by passing a current through a 100-turn coil wrapped around the tank. This creates a field that adds to that of the earth. What current should you pass through the coil, and in what direction, to produce a net field in the center of the tank that has a dip angle of 62°?

Explanation / Answer

a) This angle is below the horizontal. As one go further north, the angle increases.

b) Initial magnetic field = 41.3T

Final Magnetic field (changed by padssing current) are same with the angle diifernce between them = 62 - 48.2= 13.8

Let's fnd the resultant magnetic field

B^ 2= (41.3x 10^-6)^2 + (41.3x 10^-6)^2 - 2( 41.3x 10^-6)^2 cos 13.8 ----using cosine law

B = 10.11 x 10^-6 T apprx

I( Current) = 2piR( B)/ muN= 0.3 A apprx

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