# perfect voltage source

#### bhuvanesh

Aug 29, 2013
201
a 9 volt alkaline battery with series of 3 ohm resistor behaves as perfect voltage source

what does perfect voltage source means
that 3 ohm already present inside battery as internal,then why we have to supply externally

#### Arouse1973

Dec 18, 2013
5,178
A perfect voltage source will have zero resistance and produce an infinite current as the load goes to zero. A battery and 3Ohm resistor is far from a perfect voltage source. Also a perfect current source will have an infinite resistance and produce an infinite voltage as the load goes to infinity .

Oh just one other thing, they don't exist in real life. They are used to make circuit analysis easier.

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Your 9V battery might seem to be a perfect voltage source for high values of load resistance. In fact it might be convenient to consider it as such.

Note that along with the things Adam mentioned above, the 9V battery doesn't always have a terminal voltage of 9V and it changes with temperature, load, age, state of charge, etc.

edit: you already have the other question you asked in another post. Please don't think we're going to sit here doing your homework for you.

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