DIYbanter - View Single Post - 3 way switch. 2 switches 2 recessed lights in the hall way

micky

On Thu, 30 Jan 2014 12:51:13 -0800 (PST), wrote:

Maybe a stupid question. But I'm not a 100% sure. When people say shorted..=

Many people misuse the words short and shorted. They use them for
almost any electrical problem, but especially they use them for
'opens"** I haven't noticed people here doing that, but it's very
common.

Does this mean red on white or not wired correctly?

It's more specific than that. It might be red connected to white,
but only if that meets my definition which follows. And certainly if
two wires are connected so as to make a short, they weren't wired
correctly, but lots of mistakes are not shorts.

A short circuit is one where the current can flow from the hot to the
neutral or to the ground without passing through all of the load. Or
you can have a short which bypasses any of the other parts of a circuit.
See below****

The load is the lightbulb or the motor, or the heating elements in a
toaster, etc. The load is the reason you are using the electricity in
the first place. For light, motion, heat, etc.

Lets use an example where the load is a string of Xmas tree lights, the
old kind iiuc where if one light burned out, they all went out. You
could have a short circuit (a short) right at the plug, if the
insulation dried out and one of the wires was touching the other. Then
nothing would go to the lights, the circuit would be shorter than it
should be, (Get it? That's why it's called a short circuit.) The
current would go a quarter inch out from the plug to where the
insulation has fallen off, to the other wire, and right back into the
plug and the house wiring. It would normally blow a fuse or tirp a
breaker.

Or one lightbulb socked could be shorted. Maybe someone stuffed tinfoil
in where the bulb went. Because he didnt have any more good bulbs and
so none of them would light. That is a short. If only one bulb out
of say 40 is bypassed, the voltage will go up a little for all the other
bulbs, they will burn out a little faster, but until then they will be a
little brighter. If otoh there were only 10 bulbs, and now there are 9,
the voltage on each bulb will be 10/9ths what it's supposed to be.
Insteal of about 11 volts (110/10) it will be a little over 12 volts.
That might work too, but the bulbs will be brigher and burn out faster.
This is also a short.

Let's say somehow, you ended up bypassing 20 of the 40 bulb string.
That will double the voltage across each bulb, double the current
through the wire, make the wire get much hotter, and if the bulbs
somehow don't burn out, you'll have a heat hazard from the hot wire.
That's still a short, even though it's not bypassing the entire load. it
doesn't have to bypass the entire load, just any part of it, and it's a
short. Some shorts are very dangerous, others are not, but very very
few are desirable. The only one I can think of is the first example of
shorting out only one lightbulb socket in a string of 40.

****You can also have a short that bypasses, for example, the switch.
If a switch breaks and it is closed (the On), it's as if the switch is
shorted. Or if someone connects both of the wires to the switch to the
same screw on the switch, he's shorted out the switch. Not as big a
problem as shorting the load, but the switch won't work anymore to turn
the thing off. If the switch is broken but it's not On, it's Off,
that's called an Open. If someone takes a short wire with alligator
clips on each end and clips one to each screw on the switch, he's
shorted out the switch. People do this to bypass the switch to see if
the light etc. will turn on. If it turns on when the switch is shorted
but not when the switch is On, the switch is broken. (Not that that
applies to you. I don't think so.)

You could have a short that bypasses an antenna. If you're using
stranded flat line wire and a stray strand touches the other conductor
where it's not insultated, the two strands will be connected and almost
the entire signal from the antenna will go through the short and not to
the radio or tv. "The antenna is shorted". If one of the wires to the
antenna is broken, the antenna circuit is open.

YOu could short out the output of an amplifier. That's why there is a
plastic ridge (didn't used to be) between the two screws where one
attaches the speakers, so the strands of one side of the speaker wire
won't touch the other side. If you short out the amplifer output,
you'll blow the fuse if it has an output fuse, and if not, you'll burn
out the output transistor, and maybe the transistor before that, if
there is direct coupling. You may burn them out before the fuse blows,
even if there is a fuse.

Thanks guys for the help !

**What is an open? It is two things that should be connected but are
not, or two parts on the inside of something that should be connected
but are not. For example, in a simple light bulb, when the filament
burns out, breaks, the circuit is open, or has an open, and the bulb is
open. If you cut through a wire with a saw, you make an open.

Don't confuse open and shorted and everything else.