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Physics 2220, Summer 2016
Name:
Second Exam
Circle TA: Jessica Anthony Rohit
U of U ID:
5o L. uTTJ
4. (I) A particle of mass m and electric charge q moves perpendicular to a uniform magnetic
field of magnitude B. The particle has kinetic energy K and moves in a circle of radius r. Derive
a simplified expression for the magnitude of q in terms of the other quantities given here.
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( II ) A long cylindrical conductor of radius R carries total electric current /. The current
density, J, is not uniform over the cross-section of the conductor but is a function of the radial
distance r from the axis according to /= br2, where b is a positive constant.
(a) What are the SI units of bl
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(b) Use Ampere's law to find, in terms of terms of b, r, R, and //0 :
(i) the magnetic field, B, for 0 < r < R;
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(ii) the current/;
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(iii) the magnetic field for r > R.
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