Plane immersed in the earth's vertically downward-pointing magnetic field

AI Thread Summary
A passenger jet flying at 10 km altitude and 300 m/s in Alaska experiences a potential difference of 0.45 volts between its wing tips due to the Earth's magnetic field. The correct answer for the potential difference is option B. For determining which wingtip has a positive charge, the left wingtip is positive when viewed from the direction of travel, also confirming option B. The calculations involved using the generator formula V = L*v*B, where L is the distance between the wings. Understanding the direction of electron movement clarified the charge distribution on the wingtips.
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Homework Statement




This question and the next two refer to this situation:

http://i.imgur.com/dgJMR.png

dgJMR.png


A passenger jet is flying over Alaska in level flight at a constant altitude h = 10 km and constant speed of v = 300 m/s, immersed in the Earth's vertically downward-pointing magnetic field of B = 30 μT. The distance between the tips of the aircraft's metal wings is d = 50 m.

Part A:
Calculate the potential difference ε between the aircraft's wing tips due its motion through the Earth's magnetic field.
(a) ε = 0.0 volts
(b) ε = 0.45 volts
(c) ε = 0.90 volts

Answer is B

Part B
Which wingtip has positive charge, as viewed by a passenger in the airplane who is facing in the direction that the airplane is traveling?
(a) the right wingtip
(b) the left wingtip
(c) neither wingtip

Answer is B



Homework Equations



emf = d flux / dt

flux = int[B*dA]

The Attempt at a Solution



For part A, I tried formula above, I get answer C, because I thought I need to calculate difference for both wings? Part B I used F=BIL, however, I get the force is on right wing? What is the relationship between force ans its direction of the plane that traveling?

Thx
 
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For part A, I used the generator formula V = L*v*B = 50*300*30x10^-6 = 0.45 Volts. Had I used only one wing length I would have gotten half that voltage.

Part B is not a formula question. Use hand rules to figure out which way the electrons are pushed. Then you can tell which side is negative and which is positive.
 
Delphi51 said:
For part A, I used the generator formula V = L*v*B = 50*300*30x10^-6 = 0.45 Volts. Had I used only one wing length I would have gotten half that voltage.

Part B is not a formula question. Use hand rules to figure out which way the electrons are pushed. Then you can tell which side is negative and which is positive.

Everything makes sense now, thanks!
 
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