Can tell you come from a university background Jim, do you ask that of
applicants for courses at herts.ac?
I was asked exactly the same question when applying for Southampton Uni. in
1976.
Andy G4JNT
-----Original Message-----
From: James Moritz [SMTP:[email protected]]
Sent: 2002/11/08 11:52
To: [email protected]
Subject: Re: LF: To Ponder over the weekend
Dear Andy, LF group,
At 09:38 08/11/2002 +0000, you wrote:
This simple puzzle caused more discussion in my office this morning than it
had any right to....
Here is another conundrum along similar lines - you have two identical,
loss-free 1uF capacitors, one is charged to 10V, the other is discharged.
You then connect the two in parallel so the total C is now 2uF - charge
will flow from the charged capacitor into the discharged capacitor.
Assuming charge Q is conserved, and that Q=CV, the voltage must now be 5V.
But the stored energy in a capacitor =1/2CV^2, so with the single charged
capacitor, the stored energy is 1/2 x 1u x 100 = 50uJ, while with both
capacitors in parallel it is only 1/2 x 2u x 25 = 25uJ. So where has the
other 25uJ gone?
Cheers, Jim Moritz
73 de M0BMU
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