Blog 10: Light Bulbs, Inc.

Light bulbs are not very interesting. In fact, they can be downright annoying to replace, especially if they're in hard-to-reach areas. So how could they possibly be interesting?


We've all seen the curly CFLs, the rod-like fluorescents, and the futuristic LEDs. But the most basic of all is the incandescent. And those are the most boring of all.


Not exactly. I found two different makes of incandescents, the typical lamp bulb, and a flood-light. It was an odd experience to hold these fragile things that have hung overhead and out of reach.

Light of my life.

Big boy.

Besides the obvious size and structural differences - the flood-light is top-heavy and its sides are heavily frosted to 'focus' light outward - something completely unrelated to physical form makes the flood-light brighter: wattage. 


Okay, the flood-light is 65 W while the lamp bulb is 52W. But what does that even mean?


Well, as with everything, the inside is what matters most. Within both bulbs are filaments of tungsten. However, the flood-light's filament is thicker than that of the lamp bulb. A thicker filament provides more room for electrons to move through it, and thus enables more current to flow through the wire with a given voltage difference. More current = more power = more light!


But how much thicker is that flood-light filament? Well...


Given R = ∆V / I = (ρL) / A   -->   A = (ρLI) / (∆V)
and P = I(∆V)   -->   P / ∆V = I ,
cross-sectional area A = (ρLP) / (∆V)^2.


So if both filaments have the same ρ and L, and ∆V is constant (at 120V),


Alamp = 52(ρL) / (∆V)^2
Aflood = 65(ρL) / (∆V)^2


Therefore, the flood-light filament is 1.25 times thicker than the lamp bulb filament. When we discuss filaments, we're talking about mere millimeters (or less!). So such a minuscule difference in filament thickness really impacts the brightness of a light bulb. 

FASCINATING.

FASCINATION x 2