Fwd: Hand Battery

From: DonRath@aol.com
Date: Wed Feb 21 2001 - 12:10:33 PST

Nina -- This is the second of the three Hand Battery items (my reply to the
original). -- Don

attached mail follows:

Dear Elizabeth,

The hand battery provides very little current. Some multimeters (usually
inexpensive analog meters, with a pointer that moves) require more current to
make the pointer move than the hand battery can supply. If the multimeter has
a scale labeled 100 microamps or less (this is the same as 0.1 milliamps, or
0.1 ma), then you might be able to get a current reading. You mentioned that
your meter is a "1000m Ammeter." 1000ma is the same as 1 amp, and you won't
have a chance of getting a reading with that meter. It's just not sensistive
enough to detect the tiny current produced by the hand battery.

Try to get access to a digital multimeter -- relatively inexpensive versions
can now be found, or maybe you can borrow one. Digital meters generally
require less current to operate than analog meters. Last year, using my
digital multimeter at home with two kitchen pans, I got a noticeable current
reading on the 200 microamp scale and a noticeable voltage reading on the 2
volt scale.

One other thing to consider is the electrical contacts. I've had situations
where I was using alligator clip leads in electric circuits, and the
connection between the wire and the clip was broken -- but not visible since
it was hidden under a plastic insulated sleeve covering the body of the clip.
Also, be sure that that the metal surfaces of the foil, pans, plates, etc.
are clean -- a dirty, greasy, or badly oxidized surface could block the flow
of current.

Hope this helps.

Don Rathjen
Exploratorium Teacher Institute

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