From: Algis Sodonis (asodonis@urbanschool.org)
Date: Fri May 24 2002 - 07:40:07 PDT
Message-id: <fc.000f7611002b3dd93b9aca00c3221661.2b3de1@urbanschool.org> Date: Fri, 24 May 2002 07:40:07 -0700 Subject: Re: pinhole battery questions From: "Algis Sodonis" <asodonis@urbanschool.org>
I don't have all the answers, but here are some:
One reason a battery can't discharge all its charge at once is because it has its own internal resistance. I guess this is why if you short circuit a battery, not only will the wire heat up, but also the battery.
The battery does "try" within the limits of its own resistance to discharge all at once into the light bulb, but the light bulb's resistance is so much greater than the battery's that it limits the current at a pretty steady, slow rate.
There is a device that can discharge all its charge "at once". It is a capacitor. They are used to store charge for a flash (it takes time to charge up) and it lets the charge out all at once, which allows a small battery to create such a bright (though brief) flash.
Algis Sodonis
Urban School of SF
pinhole@exploratorium.edu writes:
>One of my brilliant students came up with some questions that I don't
>understand.
>
>If you directly connect the terminals of a battery with a wire, it
>will start to shortcircuit and heat up. Why, though, doesn't the
>battery immediately discharge when it's shortcircuited? Is it because
>the wire has a resistance and therefore can only carry a certain
>amount of amperage at once?
>
>Here's another question: if you hook up a battery to a small
>lightbulb, it can power the lightbulb for hours, until the battery
>runs dead. Why doesn't the battery immediately "try" to discharge in
>a massive burst of current, and burn out either the wires or the
>lightbulb filament?
>
>In other words, it seems like something is controlling the rate of
>discharge of the battery.
>
>Both these questions came up through studying electrochemistry, not
>through the physics side of e/m.
>
>---------------------------------------------------------------------------
>
>To unsubscribe from pinhole, send an email to requests@exploratorium.edu
>with the words 'unsubscribe pinhole' (without the quotes) in the SUBJECT
>of the email.
>
>To subscribe to the digest and only get 1 combined message a day, send an
>email to requests@exploratorium.edu with the words 'subscribe digest
>pinhole' (without the quotes) in the SUBJECT of the email.
>
>Check out what your colleagues have written on Pinhole in the Pinhole
>archives at: http://saturn.exploratorium.edu/ti/alumni/pinhole.html
>---------------------------------------------------------------------------
>
>
This archive was generated by hypermail 2.1.3 : Mon Aug 05 2002 - 09:21:41 PDT