Ohms law can't be violated in this case.  The current through the resistor
is E/R.
So, if you are outputting 10 volts, and your load is 10 ohms, the current
will be 1 amp.  If you're only
Outputting 5 volts, then you'll draw .5 amps through the resistor.  If
you're outputting 20 volts,=20
Theoretically you would draw 2 amps, but the power supply is limited to 1
amp, so you can only draw 1 amp.
The voltage will not go above this equilibrium point, and will stay at
whatever voltage it takes to maintain
The 1 amp current.  In this case, 10 volts.

Jim


-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
V G
Sent: Tuesday, November 23, 2010 2:45 PM
To: PICLIST
Subject: [EE] Question about constant current and Ohm's law

Hi all,

My understanding of analog electronics is next to nothing. But it
seems that to build a circuit of any sort, this knowledge is
essential. Well, to build a good circuit anyway.

So I have a question.

Let's say that there's a power source with variable voltage. Across
its terminals is a resistor of 10 Ohms. The power supply can only
supply a maximum of 1 Amp.

If the voltage is gradually increased, to the point where I =3D V/R > 1
Amp, what will happen? Will Ohm's "law" not be violated?

In the case of the battery charger example:

A NiMH battery should be trickle charged (assume constant current of a
few milliamps, rather than a high current pulse). The battery has a
relatively low internal resistance. How can the current supplied to
the battery be controlled precisely when the applied voltage is
relatively constant?
--=20
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--=20
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