Resistance of
One yard of copper wire, one-eighth
of an inch diameter...............................0.002 ohms.
One mile ordinary iron telegraph wire, .........10 to 20 "
Some of our selenium cells ............. 40 to 1,000,000 "
A good telegraph insulator ........... 4,000,000,000,000 "
Electro-motive force of
A pair of copper-iron junctions at a
difference of temperature of 1 deg. Fah......... =0.0000 volt.
Contact of zinc and copper ..................... =0.75 "
One Daniell's cell ............................. =1.1 "
Mr. Latimer Clark's standard cell .............. =1.45 "
One of Dr. De la Hue's batteries ...... =11,000 "
Lightning flashes probably many millions of volts.
Current measured by us in some experiments:
Using electrometer....... = almost infinitely small
currents.
Using delicate galvanometer =0.00,000,000,040 weber.
Current received from Atlantic
cable, when 25 words per minute
are being sent ................ = 0.000,001 weber
Current in ordinary land telegraph
lines ......................... = 0.003 weber
Current from dynamo machine.... = 5 to 100 weber
In any circuit, _current_ in webers = _electro-motive force_ in volts /
_resistance_ in ohms.