Re: [Phys-l] three-way bulb

[Bernard Cleyet <bernardcleyet@redshift.com>]

If you're lucky the defroster is separately fused (you have the service 
man. incdng e. schematic, don't you?),  that makes it a simple matter to 
replace it w/ a current meter or measure w/ a resistance meter *.  If 
not, one (you) may avoid cutting the wire by using an external (no 
connection) DC current meter.  I presume auto. parts stores still sell 
them.  Not very accurate; about 10% of FS, maybe better.

* Do both, the change in resistance may clue the material.

bc

p.s. it would be a bit silly to connect them is series.  We have two 
cars w/ at least one of the Joule heaters out.

Anthony Lapinski wrote:

> I'm just finishing my unit on electricity, and have three semi-related
> circuit questions dealing with everyday phenomena.
>
> 1. A three-way bulb has two filaments, often 50 W and 100 W, which can be
> connected separately or together. How is the base of such a bulb made, and
> how are the filaments wired in it?
>
> 2. I recently read that an electric blanket (with three heat settings)
> works in a similar fashion, but that the two resistive elements are
> identical. I am trying to visualize the circuit diagram. Are these
> elements wired in parallel, with switches on each side of the branch, and
> a separate wire connecting the resistors? This would allow each resistor
> to operate independently (in parallel) or together (in series).
>
> 3. An auto rear window defroster operates on 12 V. I believe the elements
> are connected in parallel, and run across much of the back window. Does
> anyone know the resistance of a given element, so I can get the total
> resistance, current, power, etc? Or is it different for each car?
>
> Thanks in advance for your insights and answers!
>
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