Physics Van 3-site Navigational Menu

Physics Van Navigational Menu

Q & A: too many batteries for bulb

Learn more physics!

Most recent answer: 03/01/2018
Q:
IF YOU USE A BULB OUT OF A 2 D CELL FLASHLIGHT IN A 3 D CELL BATTERY FLASHLIGHT, WILL IT BLOW OUT SOONER?
- NICK (age 81)
PA. USA
A:

Each D-cell supplies about 1.5 V.  Thus, the bulb is rated for 3 V.  That is, the amount of current that flows will heat the filiment to a temperature (about 2550° C = 4600° F) at which it glows with the right color light.  If you apply 4.5 V to this bulb, more current will flow, and the filiment will be hotter, making it brighter and bluer.  Also (relevant to your question) atoms of the metal filiment will "boil off" at a greater rate, because each will have, on average, more thermal kinetic energy.  So, the filament will blow out (break) more quickly.

jjt

My guess is very quickly. /mw


(published on 03/01/2018)

Follow-up on this answer.