"Tough Guy no. 1265" wrote in message
news
On Mon, 09 Nov 2015 19:08:55 -0000, Rod Speed
wrote:



"Tough Guy no. 1265" wrote in message
news
On Mon, 09 Nov 2015 17:50:30 -0000, Rod Speed
wrote:



"Tough Guy no. 1265" wrote in message
news On Mon, 09 Nov 2015 15:26:07 -0000, charles
wrote:

In article ,
Tough Guy no. 1265 wrote:
On Mon, 09 Nov 2015 13:48:44 -0000, Dave Plowman (News)
wrote:

In article ,
Tough Guy no. 1265 wrote:
Anyway, every time I've seen one of those yellow builders
transformers
for sale, it's referred to as isolating.

Of course it's isolating. That refers to the design of
transformer.

Hmmmm, isolating from the mains perhaps. I assumed isolating was
completely isolated, as in floating.

Using an auto transformer

Oh is that what they're called, I call those Variacs. Very useful.

Vsriacs have a variable ouput. Autotransfomers can be fixed.

Seems pointless. Are they cheaper than two separate coils or
something?

Corse they are, just one coil, stupid.

I dread to think how you work out how much current is flowing through
the
bit which is a primary and a secondary.

Your problem. It is in fact completely trivial to do that.

I tried to work it out for a variac once and got completely confused,

Yeah, but that's your ear to ear dog ****.

but it seems to make sense now.

Consider 240V into the whole coil and a load drawing 5 amps at 24V. Is it
true that the part of the coil between the load terminals carries 4.5A
backwards and the rest of the coil carries 0.5A forwards?

Nope.