GR9677 #88



Alternate Solutions 
evanb 20080702 13:59:18  At r = 0, the field must be zero, because an infinitelysmall amperian loop contains no current.
At r=c, the field must be zero, because the inner current and the outer current cancel out.
The only graph that satisfies these two contraints is B.  

Comments 
plapas 20090401 13:23:22  For the coaxial cable one should remember by heart that the field near the axis increases linearly and that the field outside the cable is zero (providing that equal and opposite currents run along the two parts of it). Given this, one can effortlessly to choice (B).   ssp 20080907 18:13:00  I used the condition they give us s << l... If that is true (c), (d) and (e) could approach infinity, so they are out. The in 2 in (a) seems very unphysical to be honest because we are only talking about the portion of a trajectory... So I picked (B)   evanb 20080702 13:59:18  At r = 0, the field must be zero, because an infinitelysmall amperian loop contains no current.
At r=c, the field must be zero, because the inner current and the outer current cancel out.
The only graph that satisfies these two contraints is B.
jmason86 20091004 15:21:48 
Can I get a Hell YeaAH!
Nice solution.

dogsandfrogs 20091008 15:18:42 
Simple and fantastic solution, definitely useful given the time constraint.

  sawtooth 20071030 02:24:29  For first stage, apply Ampere's law in a circle with radius 0Reply to this comment   newton 20070927 21:58:17  Amperes law,B.dl=
For r=C, ==II=0   welshmj 20070802 20:44:49  I think the part where you are finding the magnetic field between a and b is actually the magnetic field where r < a not the magnetic field where a
newton 20070927 22:13:05 
Yes i too think so.The magnetic field linearly increases in the region 0 to a.
In the region between a and b it is linearly decreasing, B=I/2r

vsravani 20081104 19:55:07 
Yes, the linearly increasing field is between 0 to r and not between ab. The error needs to be corrected.
FYI,
Between a and b, B is of the form

  yosun 20051116 23:51:57  astro_allison: subscripts and superscripts both work. however, the is due to a fileconversion error; it happens whenever a subscript or superscript ends with the letter n, as in _{n} or ^{n}. and, it's only a fileconversion error... user comment posts should not produce the error if you enter in your equation right.
please post a typoalert (in the comments section of the solution) if you find other solutions with malformed equations.   astro_allison 20051116 23:13:17  see, i can't even get it to work!   astro_allison 20051116 23:13:03  I think your subscripts aren't working for I this is in several problems. fyi  

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