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A 0.91-m aluminum bar is held with its length parallel to the east-west directio

ID: 2138628 • Letter: A

Question

A 0.91-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 17 m/s, and the emf induced across its length is 6.5 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 the number of which end of the bar is positive: 1 = east, 2 = west. A 0.91-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 17 m/s, and the emf induced across its length is 6.5 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 the number of which end of the bar is positive: 1 = east, 2 = west. Chapter 22, Problem 01 A 0.91-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 17 m/s, and the emf induced across its length is 6.5 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 the number of which end of the bar is positive: 1 = east, 2 = west.

Explanation / Answer

a)EMF = vBL

6.5x10^-4 = (17)(B)(0.91)

B = 4.2x10^-5 T


b)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. Now we can use the Right Hand Rule

Answer: East end is positive