Hi, I'm Jonathan and this is BrainStuff.
Now let's get right to it. Light bulbs are great.
They're a bright idea, right?! Eh? Eh, whatever. Anyhow it's fair to say that
they are revolutionary inventions and it's tough to imagine the modern world
without them. But they're not perfect.
Incandescent bulbs produce way more heat than they do light, and their successors,
compact fluorescent lamps (CFLs), well, they have their own disadvantages. In office
buildings across the world,
the weird buzz of CFL is slowly driving people into madness.
So, what's going on with this weird noise anyhow? Shouldn't light bulbs be like
kids in the Victorian era: seen and not heard?
Where does this "buzz" come from? Well, the buzz itself is a product of magnetostriction.
But for that to make sense, we'll need to look at how these things
actually work.
The central element in a CFL is a glass tube filled with an inert gas, usually
argon and mercury. The inside of the tube is coated with a phosphor powder, which
influences the ultimate color of the light.
There are electrodes at either end of the tube, and they're wired to an
electrical circuit. When you activate the lamp, a current moves through the
electrodes.
There's considerable voltage across the electrodes, so electrons move from one
end of the tube to the other.
Now this vaporizes the mercury, changing some of it from a liquid to a gas.
As the electrons and other charged atoms move across the tube, some of them
collide with gaseous mercury atoms.
Now these collisions excite the atoms, bumping the electrons up to the higher
energy levels. And when the electrons return to their original energy level,
they release light photons.
However, most of this is ultraviolet light. Before it becomes useful to us,
it needs to be converted to visible light. This is where that phosphor
powder comes in. The ultraviolet light causes the phosphor to fluoresce or
produce visible light.
Here's where it gets a little tricky. The current inside the tube has to be
limited so that it doesn't rise precipitously and trip the local circuit
breaker. Fluorescent lights use ballasts to keep the current in check.
Now the original ballasts for fluorescent bulbs are electromagnetic devices
similar to inductors. Imagine a bunch of wire wound around an iron core. A change
in the flow of alternate currents through the inductor creates a magnetic field.
This field also changes creating a changing voltage in the wire, slowing the
current's flow. So a ballast is useful because it prevents fluorescent lights
from, uh, blowing things up.
Think of it like a brake in a car, except that it can stop small explosions. But I
guess a brake in a car can also stop
explosions, so nevermind. That's a terrible analogy. We'll fire the writer.
The point is that the ballast can also make that buzz noise through an
effect called magnetostriction. This happens when the magnetic field produced
by the ballast physically squeezes that iron core. In the US, the light is
operating at 60 Hertz.
Thanks to magnetostriction, the core can be squeezed and released at twice that
rate (120 Hertz), creating the buzz known and often hated by office workers around
the world. Now for the next question how do you get rid of the buzz? Well, one of the
simplest solutions can be to replace the bulb itself. If you have an older
fluorescent light, you may want to replace the ballast.
But keep in mind that if the device begins to fail again,
the buzz will return. And that annoying buzz isn't the only thing people hate
about compact fluorescents. The odd colors can give people headaches, and the
mercury inside can pose some serious health risks.
Luckily, there's some good news. We're not stuck choosing between inefficient
incandescent bulbs and humming fluorescent ones. Instead, we can use LED
bulbs. Now LED bulbs may well be the light bulbs of the future, but that's a story
for a different day.