Re:

["Bob Sciamanda" <trebor@velocity.net>]

In an IDEAL transformer, the primary current is zero if the secondary is
an open circuit.  This results from the ideal primary properties of zero
resistance and infinite SELF inductance.  (Your door-bell transformer
primary is always connected to the power mains - the push-button switch
is in the secondary.)


Bob Sciamanda   trebor@velocity.net
Dept of Physics
Edinboro Univ of PA  http://www.velocity.net/~trebor
Edinboro, PA   (814)838-7185
-----Original Message-----
From: Ken Fox <kfox@stega.smoky.org>
To: Physics List <phys-l@atlantis.uwf.edu>
Date: Wednesday, April 29, 1998 11:14 PM


> A friend frowarded this question to me from a 1996 IB Physics exam. I am
> unsure how to reply to c.
>
> Any quick insights. I have some thoughts but would rather not risk the
> flames ;-). or prejudice your replies.
>
> In an ideal transformer the input is 12V 24W when connected to a
> > load and it has 100 turns. The output is 240V. Determine:
> >       a) the number of secondary turns -
> >       b) value of current in the secondary coil -
> >       c) power in the primary when the output is not connected to any
> >               resistance -
> >
> >       My Answers for the transformer ? I'm troubled with (c) question.
> >
> >       a) 2000 turns
> >       b) 0.1 A
> >       c)
>
>
> Ken Fox
> Smoky Hill High School
> 16100 Smoky Hill Rd
> Aurora,CO 80015
> 303-693-1700(w)
> 303-850-7537(H)
> kfox@stega.smoky.org