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Visit apcentral.collegeboard.com (for AP professionals) and www.collegeboard.com/apstudents (for AP students and parents). 6 AP® PHYSICS C ELECTRICITY & MAGNETISM
2005 SCORING GUIDELINES
Question 3
15 points total
(a) Distribution
of points 5 points 1 Position of End Q
(cm)
40 Measured Magnetic Field (T)
(directed from P to Q)
9.70 ¥ 10 4 n
(turns/m)
250 2 50 7.70 ¥ 10 4 200 3 60 6.80 ¥ 10 4 167 4 80 4.90 ¥ 10 4 125 5 100 4.00 ¥ 10 4 100 Trial Dividing 100 turns by the length of the spring will yield the number of turns per meter.
For each correct value of n
Two points were deducted for using more than three significant figures.
Some students used B = m0 nI and the theoretical value m0 = 4 p ¥ 10 7 (T im ) A to solve
for n. Since the question did not have any indication of using the data to obtain an
experimental value for m0 until part (c), full credit for the question could be earned for
this approach.
(b) 1 point each 2 points For correctly plotting the data from the chart
For a bestfit straight line through the plotted data points, with points both above and
below the line 1 point
1 point Copyright © 2005 by College Entrance Examination Board. All rights reserved.
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 Physics, Magnetism

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