What is the effect of the voltage variation on the life and efficiency of a tungsten filament lamp?

Within the normal range of supply voltage variations the light output will change by about 3.5\% for a 1\% change of voltage. The effect of voltage on life is much more pronounced; 5\% over-voltage will roughly halve the lamp life, whereas 5\% under-voltage will approximately double it.

Why does a filament lamp resistance change as the potential difference increases?

As the potential difference across the filament lamp increases the current across the lamp also increases due to Ohm’s law. The increase in current flow also causes the lamp to heat up which causes the resistance of the lamp to also increase.

Which filament lamp has highest efficiency?

Electrical characteristics

	120-volt lamps	230-volt lamps
Power (W)	Output (lm)	Output (lm)
5	25
15	110
25	200	230

Why does resistance increase in a filament lamp?

The resistance of a lamp increases as the temperature of its filament increases. The current flowing through a filament lamp is not directly proportional to the voltage across it.

Are filament bulbs energy efficient?

Some call them “Edison” bulbs, since they are designed to show the filament like the original light bulb invented by Thomas Edison. Did you know that many of those vintage style light bulbs use the latest LED technology? Turns out, they are extremely energy efficient!

What is the illumination efficiency of incandescent lamp?

incandescent lamps have efficiency ratings around 10 lumens/watt. Unfortunately most of the energy they consume (~90\%) goes into generating heat. Incandescent lights have the worst lifespan on the market.

Why the effective resistance of the filament is changing as it gets hotter?

This is because the filament gets hot, which causes the resistance to increase. At high temperatures, the atoms in the filament vibrate more. The electrons in the current now collide more with the atoms. More energy is needed to push the current through the filament.

Why does a coiled filament produce a brighter light?

In order to maintain the standard range of lamp wattages the power is brought back to normal by increasing wire diameter. The wire for coiled-coil filaments is therefore slightly longer and thicker than for single coils. Due to the greater mass of incandescent metal it radiates more light.

What effect of power is used in filament lamp?

Approximately 90\% of the power consumed by an incandescent light bulb is emitted as heat, rather than as visible light. Tungsten filaments radiate mostly infrared radiation at temperatures where they remain solid – below 3683 K.

Which of the lamps have more efficiency?

Luminous Efficiency is a measure of how well a light source produces visible light and the ratio of luminous flux (lumen) to power (watt)….Detailed Solution.

Type of light source	Luminous efficiency (Lumen/watt)
Incandescent bulb	8-18
Fluorescent lamp	46-75
Mercury vapour lamp	44-65
CFL	40-70

Why does temperature increase in a filament lamp?

As the current through the lamp increases, the filament gets hotter and has a higher resistance. The resistance of a filament lamp increase as the current through the filament increases and hence as the temperature increases.

How does a filament light bulb work?

In an incandescent type of bulb, an electric current is passed through a thin metal filament, heating the filament until it glows and produces light. Without this glass covering and the vacuum it helps create, the filament would overheat and oxidize in a matter or moments.