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Electromagnetism}RC Circuit

One can immediately eliminate plots A, C, E, since one would expect an exponential decay behavior for current once the switch is flipped.

More rigorously, the initial circuit with the switch S connected to a has the following equation,

Once integrated, the equation becomes,

The charge stored on the capacitor after it is fully charged is Q=CV (at t=0).

When the switch S is switched to b, the equation becomes,

where Q_0=CV from the initial connection.

Current is the negative time derivative of charge, and thus,

The initial current IS I(0)=V/R, and thus choice (B) is right.

See below for user comments and alternate solutions! See below for user comments and alternate solutions!
Alternate Solutions
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2016-10-06 21:52:37
Guys! \r\nHow can I have access to the problem, can someone help please?
2016-10-11 22:59:41
at the bottom of Alex Lang\\\\\\\'s page:\\\\r\\\\n
2016-10-11 23:01:06
at the bottom of Alex Lang\'s page:\r\n
2016-10-11 23:02:01
ignore the \\r\\n
2016-08-07 00:24:00
Eliminate the three obvious ones. Then, we are stuck between B and D. Think of r as an internal resistor to the emf charging the capacitor until it has voltage V. Then the current in second circuit is independent of r. Hence the answer is B. NEC
2013-09-23 12:24:43
Awwwww. How come there are no problems posted yet for the last two exams? :<NEC
2011-09-14 12:00:56
Where is the problem statement?
2009-05-18 03:08:59
2009-03-24 19:38:55
The EMF after switch to B must start with V/R, so only A and B are possible right. The current can not be the same all the time, eliminate A, so the right answer is B.NEC

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