You have gathered green turtle hatchlings from a beach where the magnetic field strength is 50 μT and the dip angle is 56∘. You then put the turtles in a 1.1 m diameter circular tank and monitor the direction in which they swim as you vary the magnetic field in the tank. You change the field by passing a current through a 200-turn horizontal coil wrapped around the tank. This creates a field that adds to that of the earth. Part A In what direction should current pass through the coil, to produce a net field in the center of the tank that has a dip angle of 62∘ ? In what direction should current pass through the coil, to produce a net field in the center of the tank that has a dip angle of 62 ? (a)clockwise (b)counterclockwise

Explanation:

Angle of dip = 56° , magnetic field strength = 50μT

Vertical component = 50 x sin 56 = 41.45 μT

Horizontal component = 50 cos 56 = 27.96μT

New field is added in vertical downwards direction to increase the vertical component so as to increase the angle of dip . Let this field be B

total vertical field = B +  41.45

Horizontal component = 27.96

dip angle be θ

tanθ = vertical component / horizontal component

tan62 = B +  41.45 / 27.96

1.88 = B +  41.45 / 27.96

52.58 = B +  41.45

B = 11.13 μT

Since magnetic field has to be added , current should be clockwise when looked from above.

compass can be used day and night, cloudy or sunny

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

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cathode rays were bent in the same way whenever a magnet was brought near them.