One lamp bulb blows the other doesnt

[Mikefromlondon]

as promised this is the extract from wiki;

Various lighting spectra as viewed in a diffraction grating. Upper left: fluorescent lamp, upper right: incandescent bulb, lower left: white LED, lower right: candle flame.
See also: Lamp rerating
Incandescent lamps are very sensitive to changes in the supply voltage. These characteristics are of great practical and economic importance.

For a supply voltage V near the rated voltage of the lamp:

• Light output is approximately proportional to V 3.4
• Power consumption is approximately proportional to V 1.6
• Lifetime is approximately proportional to V −16
• Color temperature is approximately proportional to V 0.42[115]

This means that a 5% reduction in operating voltage will more than double the life of the bulb, at the expense of reducing its light output by about 16%. This may be a very acceptable trade off for a light bulb that is in a difficult-to-access location (for example, traffic lights or fixtures hung from high ceilings). Long-life bulbs take advantage of this trade-off. Since the value of the electric power they consume is much more than the value of the lamp, general service lamps emphasize efficiency over long operating life. The objective is to minimize the cost of light, not the cost of lamps.[59]Early bulbs had a life of up to 2500 hours, but in 1924 a cartel agreed to limit life to 1000 hours.[116] When this was exposed in 1953, General Electric and other leading American manufacturers were banned from limiting the life.[117]

The relationships above are valid for only a few percent change of voltage around rated conditions, but they do indicate that a lamp operated at much lower than rated voltage could last for hundreds of times longer than at rated conditions, albeit with greatly reduced light output. The "Centennial Light" is a light bulb that is accepted by the Guinness Book of World Records as having been burning almost continuously at a fire station in Livermore, California, since 1901. However, the bulb emits the equivalent light of a four watt bulb. A similar story can be told of a 40-watt bulb in Texas that has been illuminated since 21 September 1908. It once resided in an opera house where notable celebrities stopped to take in its glow, and was moved to an area museum in 1977.[118]

In flood lamps used for photographic lighting, the tradeoff is made in the other direction. Compared to general-service bulbs, for the same power, these bulbs produce far more light, and (more importantly) light at a higher color temperature, at the expense of greatly reduced life (which may be as short as two hours for a type P1 lamp). The upper temperature limit for the filament is the melting point of the metal. Tungsten is the metal with the highest melting point, 3,695 K (6,191 °F). A 50-hour-life projection bulb, for instance, is designed to operate only 50 °C (122 °F) below that melting point. Such a lamp may achieve up to 22 lumens per watt, compared with 17.5 for a 750-hour general service lamp.[59]

Lamps designed for different voltages have different luminous efficacy. For example, a 100-watt, 120-volt lamp will produce about 17.1 lumens per watt. A lamp with the same rated lifetime but designed for 230 V would produce only around 12.8 lumens per watt, and a similar lamp designed for 30 volts (train lighting) would produce as much as 19.8 lumens per watt.[59] Lower voltage lamps have a thicker filament, for the same power rating. They can run hotter for the same lifetime before the filament evaporates.

The wires used to support the filament make it mechanically stronger, but remove heat, creating another tradeoff between efficiency and long life. Many general-service 120-volt lamps use no additional support wires, but lamps designed for "rough service" or "vibration service" may have as many as five. Low-voltage lamps have filaments made of heavier wire and do not require additional support wires.

Very low voltages are inefficient since the lead wires would conduct too much heat away from the filament, so the practical lower limit for incandescent lamps is 1.5 volts. Very long filaments for high voltages are fragile, and lamp bases become more difficult to insulate, so lamps for illumination are not made with rated voltages over 300 volts.[59] Some infrared heating elements are made for higher voltages, but these use tubular bulbs with widely separated terminals.

 

[Mikefromlondon]

Yes, that's what I took him to mean - but what I was asking was whether he had tried one of the apparently-blown bulbs in the small light.
Thanks - I just wish that everyone would, always I have so often pointed out how much confusion can result from talking about "the lamp in the lamp", or asking for "a lamp for the lamp", but that's exactly what has been happening here!!

Kind Regards, John

I have always called them bulbs too, like I would say to my wife "where did you keep my bulbs! and she would say which ones?

 

[Mikefromlondon]

Although I can't advise OP but if it was my lamp, and it kept blowing bulbs, I would run it through a current limited power source, where no matter when you switch on, it would limit peak current to just a little over its running current, and it can be done using some simple parts housed in a well protected box and against risk from overheating or shorts and protected by low value fuse as well.

 

[333rocky333]

as promised this is the extract from wiki;

Various lighting spectra as viewed in a diffraction grating. Upper left: fluorescent lamp, upper right: incandescent bulb, lower left: white LED, lower right: candle flame.
See also: Lamp rerating
Incandescent lamps are very sensitive to changes in the supply voltage. These characteristics are of great practical and economic importance.

For a supply voltage V near the rated voltage of the lamp:

• Light output is approximately proportional to V 3.4
• Power consumption is approximately proportional to V 1.6
• Lifetime is approximately proportional to V −16
• Color temperature is approximately proportional to V 0.42[115]

This means that a 5% reduction in operating voltage will more than double the life of the bulb, at the expense of reducing its light output by about 16%. This may be a very acceptable trade off for a light bulb that is in a difficult-to-access location (for example, traffic lights or fixtures hung from high ceilings). Long-life bulbs take advantage of this trade-off. Since the value of the electric power they consume is much more than the value of the lamp, general service lamps emphasize efficiency over long operating life. The objective is to minimize the cost of light, not the cost of lamps.[59]Early bulbs had a life of up to 2500 hours, but in 1924 a cartel agreed to limit life to 1000 hours.[116] When this was exposed in 1953, General Electric and other leading American manufacturers were banned from limiting the life.[117]

The relationships above are valid for only a few percent change of voltage around rated conditions, but they do indicate that a lamp operated at much lower than rated voltage could last for hundreds of times longer than at rated conditions, albeit with greatly reduced light output. The "Centennial Light" is a light bulb that is accepted by the Guinness Book of World Records as having been burning almost continuously at a fire station in Livermore, California, since 1901. However, the bulb emits the equivalent light of a four watt bulb. A similar story can be told of a 40-watt bulb in Texas that has been illuminated since 21 September 1908. It once resided in an opera house where notable celebrities stopped to take in its glow, and was moved to an area museum in 1977.[118]

In flood lamps used for photographic lighting, the tradeoff is made in the other direction. Compared to general-service bulbs, for the same power, these bulbs produce far more light, and (more importantly) light at a higher color temperature, at the expense of greatly reduced life (which may be as short as two hours for a type P1 lamp). The upper temperature limit for the filament is the melting point of the metal. Tungsten is the metal with the highest melting point, 3,695 K (6,191 °F). A 50-hour-life projection bulb, for instance, is designed to operate only 50 °C (122 °F) below that melting point. Such a lamp may achieve up to 22 lumens per watt, compared with 17.5 for a 750-hour general service lamp.[59]

Lamps designed for different voltages have different luminous efficacy. For example, a 100-watt, 120-volt lamp will produce about 17.1 lumens per watt. A lamp with the same rated lifetime but designed for 230 V would produce only around 12.8 lumens per watt, and a similar lamp designed for 30 volts (train lighting) would produce as much as 19.8 lumens per watt.[59] Lower voltage lamps have a thicker filament, for the same power rating. They can run hotter for the same lifetime before the filament evaporates.

The wires used to support the filament make it mechanically stronger, but remove heat, creating another tradeoff between efficiency and long life. Many general-service 120-volt lamps use no additional support wires, but lamps designed for "rough service" or "vibration service" may have as many as five. Low-voltage lamps have filaments made of heavier wire and do not require additional support wires.

Very low voltages are inefficient since the lead wires would conduct too much heat away from the filament, so the practical lower limit for incandescent lamps is 1.5 volts. Very long filaments for high voltages are fragile, and lamp bases become more difficult to insulate, so lamps for illumination are not made with rated voltages over 300 volts.[59] Some infrared heating elements are made for higher voltages, but these use tubular bulbs with widely separated terminals.

I would quess that John Lewis supply Halogen bulbs nowadays, so not sure how relevant that all is

 

[JohnW2]

Although I can't advise OP but if it was my lamp, and it kept blowing bulbs, I would run it through a current limited power source, where no matter when you switch on, it would limit peak current to just a little over its running current, and it can be done using some simple parts housed in a well protected box and against risk from overheating or shorts and protected by low value fuse as well.

Even if the OP had the ability to construct such a power source, that would surely be a ludicrously OTT way of addressing his problem with light bulbs!

Kind Regards, John

 

[Mikefromlondon]

@333rocky, You missed the point I was making about all filament lamps including halogens, can give far less light by a small reduction in voltage supply and in the same way a small increase in voltage can equally make them more suspectable to much reduced life and giving more brighter output. This is not the original article i read long while ago, but this wiki article also confirms this.

 

[Mikefromlondon]

Even if the OP had the ability to construct such a power source, that would surely be a ludicrously OTT way of addressing his problem with light bulbs!

Kind Regards, John

I respect your opinion John. Mine is opposite. I would do that to save spending so much on bulbs.

 

[JohnW2]

I respect your opinion John. Mine is opposite. I would do that to save spending so much on bulbs.

If you were using mainly filament bulbs, would you do that for each and every one of your light fittings? If you did, you would undoubtedly reducing your spending on light bulbs to some extent, but .....!!

Kind Regards, John

 

[Mikefromlondon]

I guess not John, Nope, I noticed that my 60watt candle lights were far more vulnerable to blowing up more frequently than 100watt bulbs, again not 100% sure why, but we can put it down to many factors, like different construction, manufacturer's and so on and as well as different conditions within your house and different wiring lengths and so on, but only if i wanted a prized table lamp or a stand lamp to be as I wanted then may just for one such item.

Now I don't get that problem as I now use energy saving lamps that I thank my mate for picking up for me from Robert Dyas ( just remembered the name of that store) that had special sale of these energy saving lamps 10p each made by Philips. This was a good 5 to 7 years ago now.