Why don't you get electrocuted by these things?

[FreshAL]

https://www.farnsworthelectronics.com/part%20images/multim8.gif

Electrical testing screwdrivers with a bulb in the handle that tells you if a wire is live when you pop your thumb on the end.

So why don't you get fried?

[Hetzer]

The handle is made of plastic.
____________________
"There's the horizon! Ride hard, ride fast and cut down all who stand in your way!"

[Dazbo666]

because the handle is insulated from the live parts
____________________
1st bike (Sept'06 - May'10) : 1991 GPZ500S / Current bike (since Nov 2009) : 2003 Suzuki Bandit 600N
Word of the day : DILLIGAF

[Dragonfly]

Even i knew that
____________________
All the breast.
Muzza on Binge:
He's too busy beating the everloving shit out of Lizzie to notice this thread has taken a turn down Drama Avenue and stopped off at the popcorn shop.

[FreshAL]

So why do you have to touch the metal bit on the end before it works?

Aren't you becoming part of the circuit?

Presumably there has to be some current flowing to light the bulb. The screwdriver is only touching one wire, so the current must be flowing through you.

I repeat the original question - why don't you get fried?

[Hetzer]

Assuming it'll test 240v circuits, the fact the bulb doesn't pop would indicate there's some serious resistance going on, hence no electric shock to the user.

But I know next to nothing about elctct...elakt...magic.
____________________
"There's the horizon! Ride hard, ride fast and cut down all who stand in your way!"

[Barry_M2]

[pa_broon74]

Do you know...

This is one of those weird questions, I've got an HND in electrical and electronic engineering and I don't know the answer either

I think its just because I haven't ever thought about it, also, we always used multimeters.

However, I imagine as Hetzer pointed out there'll be a pretty massive resister or perhaps the neon bulb itself willl have resistive properties. When you place your thumb on the top contact you're providing a route to earth thus completing the circuit. You don't get fried due to the tiny amount of current left after the resistive element does its job.

I think... (It might also be sorcery... )

[Didge]

This is one of the things I've often wondered. I think pa_broon74 is correct, but I stand to be corrected by an electrickery type person.

[Sparks!]

The handle is insulated from live parts so you don't directly contact 240 volts. The tip goes through to the center of handle where there is a resistor which obviously drops the current. You touch the metal disc on the end of the driver, you are standing on ground so you provide an earth which creates a circuit and will light the bulb if a voltage is present.

Voltage doesn't kill, ampage does. The lower the resistance, more amps will flow, which is good in terms of electrical safety because in a short circuit fault a high ampage will flow which will trip the circuit breaker a lot quicker. That's why it's important to make sure all connections are secure and tight with a minimum number of connectsons (i.e avoid junction boxes etc where possible)

Anyawy, point I'm getting at is the resistor will bring the amps down to a safe level which is why you don't get a shock.

I am not 100% that this is correct, I have never used one as they aren't really all that safe... if they get wet or somehow fill up with water then the resistor will be bypassed and you'll get a shock This is just how I gather that they work.
____________________
Current Toys: 06 Yamaha WR250F | Nissan 350Z GT | Tech 4 Homes

[tatters]

Chuck it in the bin and buy a proper volt stick or multimeter, a number of people have been hurt by faulty ones in the past.
____________________
Past:NRG50,AF1125(x2),NSR125RR,ZZR250,CX500,VFR400,KR1S,ZZR600(x2),CB400N,YZF1000(x2),KH125,Z200,FX400R,CBR954RR(x2)GPZ500S,GT550,VFR750F(x2),RD350N,XR650R,CBR600F,CB250,KDX250,YZF750R,CRM250,400EXC,KLR650,TTR600RE,DR350S,R100GSPD,RGV250,VMAX1200,DL650,KZ750 Present:G650XC,C12,CRF450X,1190ADV

[-Savage-]

I've always wondered too, I must admit i would have reservations about testing mains with it lol. Just in case .
____________________
My Bikes - - - Royal Enfield 500 with sidecar, VFR800, CBR600FX,
Peugeot Speedfight 100, Kymco Hipster 125, GSXR750K5, Jawa TS 350

[carvell]

[Sparks!]

[KevTM]

if you don't know what you're doing don't start prodding the mains with metallic sticks. mmmkay.

[Walloper]

For the same reason that you can tell who is calling if you look at the screen of your mobile when it rings.


There is no exact answer.

There has been magical stuff like this going on since time began.
____________________
W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair

[ZRX61]

[firefox]

If you look close there is a resitor in the screw drivers, you can touch a high voltage and be fine as long as the ampage isnt high, if you feel tempted get one of those screw drivers, get a multi meter, put the neg of the meter on the top of the screw driver and the pos to the same place you are testing it should tell you how much comes through to your finger.
____________________
bye bye gti <^>( ' . ' )<^>
*officer* what caused the crash ? *firefox* you see that wall up there sir ?
*officer* yes what about it *firefox* i tooted my horn but it refused to move i had to teach it a lesson.

[Walloper]

To test if the resistor is the part doing all the work.

Stick the screwdriver into a 13amp outlet and touch the end.

Compare this to sticking a 4" nail into the same 13amp outlet.


____________________
W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair

[nick606]

hokies theres a resistor so you dont get fried.

there was a case how ever of a man who had one for years never replaced the insulation deteriorated his apprentice used it accidentally drop it in water took it out dryed it off though it would be fine the man then came to use it later the water bypassed the resistor shocked him and he died.

there are better and safer ways to see if something is live. There is something out now called a magic pen or something. you hold it up to a wire and if it lights up its live. It even works threw walls. (It works by magnetic field)

[Cigaro]

Because it's going through a neon bulb, which has an incredibly high internal resistance, and only a tiny amount of current is required to light it.

It will also light up if you take it near a plasma ball, it's the same kind of thing.

[pa_broon74]

TBH I wouldn't use one to test mains either. I'd just plug something in that I knew worked.

They are handy if you use a terminal screwdriver often though. If you insist on having something to test mains, get one of these:

[Walloper]

You could also drag a washing machine over and plug it in.
If the wee red light comes on you can be sure you have power.

A lot safer than dicking around with test equipment you do not fully understand.

Remember:

Electricians are the only folk who are smart enough to work on electrics.
____________________
W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair

[pwntifex]