The typical resistance of the tungsten filament of a 60 wattincandescent light b

Question

The typical resistance of the tungsten filament of a 60 wattincandescent light bulb when it is turned off is 24 ohms and itsresistance when operating from a 120 volt power source is 240ohms. Generally, an incandescdent light bulb filament is mostlikely to "burn out" when it is first turned on than at any othertime. Explain why? Hint; Calculate the power dissipated whenfirst turned on. The typical resistance of the tungsten filament of a 60 wattincandescent light bulb when it is turned off is 24 ohms and itsresistance when operating from a 120 volt power source is 240ohms. Generally, an incandescdent light bulb filament is mostlikely to "burn out" when it is first turned on than at any othertime. Explain why? Hint; Calculate the power dissipated whenfirst turned on.

Explanation / Answer

The resistance is lower when the bulb is first turned on, andincreases as the light heats up. This means that maxmum current isavailable when the light is first turned on. Because of this, whenmaximum current is drawn by the light is the most likely time thatthe filament will open. As the hint indicates, if you calculatepower you can see how the current and power are associated: Power is: P = V*I and I is found by I =V/R we find that power when the bulb is first turned on, 24is: P = 120*(120/24) P = 120 * 5 P = 600 watts and when the bulb is heated, 240, is: P = 120*(120/240) P = 120 * .5 P = 60 watts As the resistance increases, the current and powerdecrease. Hope this helps. P = 120*(120/240) P = 120 * .5 P = 60 watts As the resistance increases, the current and powerdecrease. Hope this helps.

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