As shown below, a metal wire of mass m = 24.1 mg can slide with negligible frict
ID: 1263079 • Letter: A
Question
As shown below, a metal wire of mass m = 24.1 mg can slide with negligible friction on two horizontal parallel rails separated by a distance d = 2.56 cm. The track lies in a vertical uniform magnetic field of magnitude B = 56.3 mT. At time t = O, device G is connected to the rails, producing a constant current I = 9.13 mA in the wire and rails (even as the wire moves). (a) Describe how you expect the wire to move after the current starts flowing (direction? constant or increasing velocity?). Explain your reasoning. (h) At t = 61.1 ms, what is the speed of the wire?Explanation / Answer
a)
Direction is left
The direction of current in the wire is pointing vertically up then a positive charge would experience a force to the right but electrons are negative so the force is to the left
b)
Magnetic force
F=BILsin90 =BId
F=(56.3*10-3)*(9.13*10-3)*(0.0256)
F=1.316*10-5 N
acceleration
a=F/m =(1.316*10-5)/(24.1*10-6)
a=0.546 m/s2
So speed of the wire is
V=a*t =(0.546)(61.1*10-3)
V=0.0334 m/s or 3.34 cm/s
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