a simple question

[JWelectric]

Thank you for the post and the numbers concerning the number of death annually due to electrocution.

When displaying those numbers as a whole to show that more people die annually from smoking or car accidents than from electrocution it doesn’t look very bad or dangerous.

But on a side note;
If even one of them was one of my family members I don’t think those numbers would have very much meaning to me. If one of those numbers was me I don’t think my children would much care about those numbers either.

Now couple all those numbers together with the total number of people that smoke daily and those that drive daily with the total number of do-it-yourselfers that are working on live electrical circuits daily and the ratio looks drastically different.

Again thank you for those numbers as even 1300 annually is way two many for something that can be avoided.

 

[Sjsmithjr]

Now couple all those numbers together with the total number of people that smoke daily and those that drive daily with the total number of do-it-yourselfers that are working on live electrical circuits daily and the ratio looks drastically different.

Yep. Also consider that of the 1300 deaths attributed to electrocution, only 135 or so were work related deaths. That ratio doesn't work out so well for the inexperienced either.

 

[Sponsor]

 

[Alectrician]

I still think it's a trick question.

I still want to know why the bulbs don't burn out?

Anybody?

240V thru a 120V filiment?

Anybody?

 

[Jimbo]

It is NOT 240 through a 120 filament. It is 240 through TWO 120 filaments in series. As mentioned, the lower wattage bulb will receive somewhat more than its rated current, so will have a shorter life, but would not usually blow immediately.

 

[Jadnashua]

Voltage drops across resisters in series based on their ratio of resistance...the higher the resistance, the larger the voltage drop across it. More resistance, more voltage. A short is like a zero resistance resistor...no voltage drop across (or along, if you prefer). All wires have some resistance, so if you have a good enough meter, you can measure it.

 

[MaintenanceGuy]

....
Here is a problem for some of you to think about and see if you can come up with an answer....

Unless you can answer this question and explain why then you should be asking yourself if you should be messing with an electrical circuit.
Should you come in contact with a 120 volt circuit the same will happen to you as happens with these two bulbs.

I disagree with this statement because I didn't know which would burn brighter.

I can quickly calculate the current through each bulb and I can see that the 40W bulb would be brighter than usual and the 100W bulb would be dimmer than usual but that doesn't mean that the 40W bulb would be brighter than the 100W bulb.

The problem isn't a lack of understanding of electric. I just don't know the relationship between current and lumen output or even the relationship between lumen output and perceived brightness.

 

[Seaneys]

Yep. Also consider that of the 1300 deaths attributed to electrocution, only 135 or so were work related deaths. That ratio doesn't work out so well for the inexperienced either.

I'm not sure you can relate this to DIY'er.

Is there anything to indicate they weren't simply using their hair dryer in the shower?

 

[JWelectric]

I disagree with this statement because I didn't know which would burn brighter.

I can quickly calculate the current through each bulb and I can see that the 40W bulb would be brighter than usual and the 100W bulb would be dimmer than usual but that doesn't mean that the 40W bulb would be brighter than the 100W bulb.

The problem isn't a lack of understanding of electric. I just don't know the relationship between current and lumen output or even the relationship between lumen output and perceived brightness.

It is okay if you want to disagree with me and I am sure that there are many that does.

If you don't know the relationship between lumen and current the answer can be found by clicking here

 

[JWelectric]

I'm not sure you can relate this to DIY'er.

Is there anything to indicate they weren't simply using their hair dryer in the shower?

I would say this would fall under the inexperienced

 

[Sjsmithjr]

I would say this would fall under the inexperienced

Yep. One should also consider that some number of the 135 workplace fatalities were not qualified electricians. We are constantly reminding our guys in the field that unless they are a qualified electrician that they are not to attempt electrical work of any kind.

 

[Thatguy]

Fwiw

Wiki says incand. lamp power is proportional to V^(1.6).

Based on this, I for a 100w bulb = .047[V1^(0.6)] and I for a 50w bulb = .024[V2^(0.6)], with V1 and V2 the voltage across each, respectively.

Since current is the same in a series circuit, these two equations must be equal to each other, and V1 + V2 must equal 240v.

By trial and error, my spreadsheet tells me that the 100w bulb has 57v across it and the 50w has 183v across it. I'm too lazy to solve it the other way.

There is also the issue of luminous efficiency, but I think with this voltage difference the 50w will shine brilliantly for its very short life.

 

[Seaneys]

Yep. One should also consider that some number of the 135 workplace fatalities were not qualified electricians. We are constantly reminding our guys in the field that unless they are a qualified electrician that they are not to attempt electrical work of any kind.

Hmmm.. Are you sure? The only two people I know of who were killed by electrocution were electricians. One was a friends dad from high school, the other was a lineman at our local power company.

The death of the lineman is hearsay I guess, but the source was one of his team members.

Steve

 

[Sjsmithjr]

Hmmm.. Are you sure? The only two people I know of who were killed by electrocution were electricians. One was a friends dad from high school, the other was a lineman at our local power company.

The death of the lineman is hearsay I guess, but the source was one of his team members.

Steve

Actually, I was incorrect about the number of fatalities. About one worker (as opposed to electrician) dies every day as a result of electrical hazards while 135 died last year from contact with power lines. OSHA revised their electrical installation standards last year, noting that "while not the leading cause of workplace deaths, electrical accidents are disproportionately fatal when they do occur."

Also to clarify, our companies policy is that only a qualified electrician can perform electrical work. That means that the qualified electrician (meaning someone licensed in the state we are working) has to actually perform the work; he can't tell Steve to connect the black wire here, the white wire there, and do the hokey pokey. This isn't our policy because we're nice guys - if our LWCIR (feel free to google it) gets to high we'll be out of business.

By the way Steve, forgive me if I wasn't paying attention, but what exactly is your area of expertise again?

 

[Alectrician]

It is NOT 240 through a 120 filament. It is 240 through TWO 120 filaments in series. As mentioned, the lower wattage bulb will receive somewhat more than its rated current, so will have a shorter life, but would not usually blow immediately.

One filament, two filaments...I still think it would burn out immeadiatly. I'll try it someday soon.

And why do you say it would not usually blow out immeadiately?

 

[JWelectric]

One filament, two filaments...I still think it would burn out immeadiatly. I'll try it someday soon.

Until the filament gets to the melting point it will emit light. This may burn like this for several hours before blowing

And why do you say it would not usually blow out immeadiately?

The main reason I will say it won’t burn out immediately is because I have done it no less that 27 times in the past 9 years. That is three classes a year for the past nine years. You can do the same experiment with 120 volts wired in series.

 

[DX]

Thatguy gets the prize for most thorough understanding and knowledge of electricity. He actually calculated the voltages.

jwelectric gets the prize for most astute lightbulb shopper He actually found bulbs that withstand 183V for at least the duration of a lab session! That bulb dissipates 1.96 times its rated power.

 

[Dunbar Plumbing]

Crispy Strips!​

Got a Ground?​

Honey, What in the world did you flush?​

Whoops!​

 

[Mikey]

A slightly trickier question

This may deserve another thread, but if we were all sitting around discussing the 100W/50W thing over a few beers, I would bring up this puzzler eventually, so here goes:

At the bar of the Magic Castle in Hollywood there is a display consisting of a standard line cord feeding 4 devices mounted on a wooden board. All wiring is exposed, and everything is in series as follows:

Hot side of the line cord -> Red knife switch -> light socket with red bulb in it -> Green knife switch -> light socket with green bulb in it -> neutral side of line cord.

Starting out with the thing plugged into a standard 120VAC receptacle, both knife switches open, both bulbs are out.
-close the red switch: the red bulb lights.
-close the green switch: the green bulb lights (red bulb stays lit).
-open the red switch: red bulb goes out (green bulb stays lit).
-open the green switch: green bulb goes out.

Now interchange the bulbs, so that the green bulb is where the red one used to be, and vice-versa. Again,
-close the red switch: the red bulb lights.
-close the green switch: the green bulb lights (red bulb stays lit).
-open the red switch: red bulb goes out (green bulb stays lit).
-open the green switch: green bulb goes out.

Explain.

 

[JWelectric]

This may deserve another thread, but if we were all sitting around discussing the 100W/50W thing over a few beers, I would bring up this puzzler eventually, so here goes:

At the bar of the Magic Castle in Hollywood there is a display consisting of a standard line cord feeding 4 devices mounted on a wooden board. All wiring is exposed, and everything is in series as follows:

Hot side of the line cord -> Red knife switch -> light socket with red bulb in it -> Green knife switch -> light socket with green bulb in it -> neutral side of line cord.

Starting out with the thing plugged into a standard 120VAC receptacle, both knife switches open, both bulbs are out.
-close the red switch: the red bulb lights.
-close the green switch: the green bulb lights (red bulb stays lit).
-open the red switch: red bulb goes out (green bulb stays lit).
-open the green switch: green bulb goes out.

Now interchange the bulbs, so that the green bulb is where the red one used to be, and vice-versa. Again,
-close the red switch: the red bulb lights.
-close the green switch: the green bulb lights (red bulb stays lit).
-open the red switch: red bulb goes out (green bulb stays lit).
-open the green switch: green bulb goes out.

Explain.

It is magic

 

[Thatguy]

standard line cord feeding 4 devices mounted on a wooden board.
All wiring is exposed, and everything is in series as follows:

Hot side of the line cord -> Red knife switch -> light socket with red bulb in it -> Green knife switch -> light socket with green bulb in it -> neutral side of line cord.

Starting out with the thing plugged into a standard 120VAC receptacle, both knife switches open, both bulbs are out.
-close the red switch: the red bulb lights.
Violates Ohm's law.

I say, Hoax.