[TCML] Re: Franklins bells

[David Speck]

Jolyon,

If you understand how Franklin's bells work, you would understand why 
you need DC, not AC.

When the swinging clapper contacts the high voltage charged terminal, it 
conducts electrons onto its surface until it has the same charge density 
as the main terminal.  Since like charges repel, the moving clapper is 
then pushed away from the fixed terminal.  When it hits the grounded 
terminal, it loses its charge to ground, and then bounces back toward 
the HV terminal, and the process repeats as long as the HV is present.

If you have AC on the HV terminal, then the charge on the HV fixed 
terminal is varying much faster than the travel time of the moving 
clapper between the bells, and equally in both polarities.   There would 
be no net force on the moving clapper, though it would vibrate back and 
forth a tiny bit.

I suppose that if you had a really tiny, very light clapper, and a very 
high applied AC voltage, you could make the system oscillate faster than 
the frequency of the applied AC, but I bet that  you would probably just 
end up with an arc between the HV and ground fixed electrodes.

Dave

On 4/11/2012 4:24 PM, vatercox at aol.com wrote:
> Why the need to rectify? Surely AC exhibits the same properties of attraction/ repulsion as DC so there should be no need and the bells should ring just as easily either way. Doesn't AC cause a deflection on a gold[leaf electroscope?
>
> Yours perplexedly,
> Jolyon