A 0.75-m aluminum bar is held with its length parallel to the east-west directio

Question

A 0.75-m aluminum bar is held with its length parallel to the east-west direction and dropped from a bridge. Just before the bar hits the river below, its speed is 16 m/s, and the emf induced across its length is 7.4 x 10-4 V. Assuming the horizontal component of the Earth's magnetic field at the location of the bar points directly north, (a) determine the magnitude of the horizontal component of the Earth's magnetic field, and (b) state whether the east end or the west end of the bar is positive

Explanation / Answer

Here

length of bar, l = 0.75 m
velocity before hitting river bed, v = 16 m/s
Induced EMF, EMF = 7.4 * 10^-4 V

pART a:
sINCE emf = V*b*l

Solving for magnatic field, B

B = EMF/v*l
B = 7.4 * 10^-4 / (16 * 0.75)
B = 6.167*10^-5 T

Part B:
since Magnetic field lines go from the North pole to the south pole. Magnetic North pole is near the geographic South pole, therefore the Earth's magnetic field lines go from the geographic South to geographic North.Therefore East end is positive

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