Unformatted text preview: he moment you release the rod from rest).
(Note, the bar is sliding on frictionless rails).
Initially, there is no motional emf because
there is no motion, so acceleration
depends on battery voltage, resistance,
magnetic field, and mass of the rod. Doubling R cuts initial acceleration in half. A)
B)
C)
D)
E) vt is half and a0 half
vt is twice and a0 twice
vt is half and a0 is the same
vt is the same and a0 half
vt is the same and a0 is the same Terminal velocity occurs when the motional
emf cancels the battery emf and reduces the
current (and hence the magnetic force) to zero.
Since current is zero at terminal velocity the
resistance is irrelevant. Version 1 Page 5 10. The solid circle of radius R in the diagram shows the cross section of a long solenoid with
its axis pointing straight into the page. The current in the solenoid is increasing steadily.
The dashed concentric circles are four integration paths in a plane perpendicular to the
solenoid axis that have radii of r1 = R/4, r2 = R/2, r3 =2R, and r4 = 3R. Rank the paths
according to the magnitude of the circulation of the electric field, E dl along each
path, least to greatest. R 1 A)
B)
C)
D)
E) 2 3 4 The circulation is the integral on the left side
of Faraday's law (as defined in the problem).
Basically, you need to compare the
circulations by looking at the right side of
Faraday's law. Path 3 and 4 tie because
there is no flux outside the solenoid and they
both surround all of the flux inside. Path 2 is
larger than pat...
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 Fall '08
 DaveWinn
 Physics, Magnetic Field

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