38
votes
Accepted
What are the little bits of metal that come out of light bulb filaments and why do they stick to only one terminal?
Those are beautiful photomicrographs! Awesome to see those things up close!
What are these little bits of metal (are they metal whiskers like tin whiskers), did they come from the filament or the ...
22
votes
Accepted
Neon lamp symbol
Neon lamps are not polarised but only the more negative electrode will light up.
Figure 1. Only the cathode lights up. +DC (left), -DC (center), AC (right) supplied to NE-2 type neon lamps. Source: ...
- 180k
19
votes
Accepted
What explains this bulb/motor behavior?
For an ideal motor, speed and voltage are proportional to each other, as are current and torque.
A small low voltage motor will be far from ideal, but the general relationship still holds.
With no ...
- 174k
16
votes
What are the little bits of metal that come out of light bulb filaments and why do they stick to only one terminal?
This is a tungsten-halogen bulb, isn't it?
Normal (tungsten + inert gas or vacuum) bulbs don't have these crystals. Their glass gets uniformly black until enough tungsten migrates from the filament ...
- 9,686
14
votes
Neon lamp symbol
The dot denotes a gas-filled tube, which distinguishes it from a normal vacuum tube. Neon bulbs and voltage regulator tubes1, as well as certain types of high-power tubes such as thyratrons and ...
- 178k
9
votes
Accepted
filament led bulb inrush current
Look at the listed amp rating of your bulb
You need to look at your bulb's documentation/data sheet for its listed draw in amps. If it provides a VA rating, you can compute amps from VA/volts. If ...
9
votes
Why does a neon lamp indicator on a power strip switch flicker in the dark?
Responding to old post but it comes up at top of google search:
Neon lights can't work in complete darkness. This is the "neon lamp dark effect".
I know it sounds fake, but that's why neon ...
9
votes
Why did a spark occur between my HDMI cable and metal lamp base?
If everything had been working previously in some configuration with the HDMI cable plugged in at both ends then my best guess is that there is a fault in your lamp. Maybe an earth has become detached ...
- 2,512
8
votes
I need to test multiple lights that turn on individually using a single switch. I don't understand the use of diodes in this diagram
The lamp test button will work in your example schematic, however the diodes will only allow the positive half of the AC cycle through, so the lamps will not be at full brightness when being tested.
- 4,050
7
votes
Why plug is polarized in the US? What are the benefits?
It's more than that -- polarized plug make cheap single-pole switches much safer.
For example, look at the extension strip:
With a polarized plug, it is perfectly safe to have a single-pole switch ...
- 3,278
7
votes
What explains this bulb/motor behavior?
but beyond wildly guessing that the motor increases the circuit's
current as it has to work harder I couldn't get very far.
It's a good guess because it is correct.
The motor draws more current ...
- 473k
6
votes
Accepted
Can I use a single LED from a 220V LED light bulb to repair my 1.5V LED flashlight?
With demand for more TV backlight LEDs, production of < 3V white LEDs now offers 6V, 9V. These are chips with cascaded single diode multiples of 3V and look identical on 2835 SMD, unless you look ...
- 148k
6
votes
Why did a spark occur between my HDMI cable and metal lamp base?
If you aren't in the US, ignore this answer. Also, be very careful with live outlets.
The problem could be a miswired plug. You can buy an outlet tester for a few bucks at a hardware store. They light ...
- 351
6
votes
I need to test multiple lights that turn on individually using a single switch. I don't understand the use of diodes in this diagram
As previous answers have stated, diodes are used to block voltage between lamps when lamptest is not closed, and you don´t have so many individual lamptest contacts for each lamp. The setup works fine ...
- 1,787
5
votes
Will repeatedly turning a light bulb on and off damage it?
According to the U.S. Dept. of Energy:
It is best to turn off incandescent and halogen bulbs whenever they
are not needed, due to their high consumption of electricity.
For a compact fluorescent bulb,...
- 51
5
votes
Still 1000 hours of lifetime
The (now obsolescent) conventional tungsten-filament consumer incandescent bulbs have a trade-off between life and efficiency.
The longer you make the bulb last for (by running the filament cooler) ...
5
votes
Why would an incandescent bulb produce a bright flash when burning out?
TL;DR The electric arc may conduct much higher current than the filament, this is not normal mode of bulb operation so you can see a flash and maybe even have the bulb exploded.
Typical incandescent ...
- 12.5k
5
votes
Accepted
What happens if I power a 12 V LED lamp at twice its voltage with a 24 V power supply?
If it is a constant current driver, it will drive the LED with constant current and the LED voltage ends up being 12V or whatever it happens to be with the LED.
So the output voltage to LED must be ...
- 172k
5
votes
Double envelope bulbs
Just what it says. There are two envelopes, the internal quartz capsule containing the filament and halogen that gets very hot and an external one that does not get as hot.
I would guess this is for ...
5
votes
Can I power a 12v pea bulb with a 9v battery?
No, it would be much brighter but would last much less time. A primary alkaline AA cell of good quality might be 2000-3000mAh. A 9V alkaline battery will be much less, maybe 600mAh. And the lamp will ...
4
votes
Replace lamp in old amplifier
Just rotate the plastic from the back (CCW to "unscrew", it's sort of a bayonet base-like action). I have the same general kind of lamp in the instrument cluster of an E28 chassis automobile. The ...
4
votes
Why plug is polarized in the US? What are the benefits?
The reason is historical. WAAY back in the old days the neutral was used as a ground. My dad grew up in the 30s and it he said it was very common for washing machines and drills and light fixtures ...
- 931
4
votes
Wiring 1 lamp and 1 fan to 2 switches instead of 1
I've then proceeded to various mix/matches, sometimes the fuse would pop and I would have to reset it.
This is really bad and very stupid. You are messing with mains electricity with zero ...
- 180k
4
votes
Why did a spark occur between my HDMI cable and metal lamp base?
The crater shows enough energy was released to vaporize metal. This means the usual causes of small sparks and shocks, like line filter capacitors, are not involved here. This looks like what happens ...
- 81.6k
4
votes
What explains this bulb/motor behavior?
To add to the other responses. When the motor is starting up (no fan) it accelerates until the motors back EMF equals the battery voltage. At this point the motor spins at steady state speed and ...
- 536
4
votes
What are the little bits of metal that come out of light bulb filaments and why do they stick to only one terminal?
Others have explained the broad strokes of the mechanisms at play here, so I'll address the one noted peculiarity: growth on the connection rod / electrode.
This may simply be that, being longer, it ...
- 45.6k
3
votes
Accepted
Two or more Diac Triac dimmers in parallel
Parallel connection of 2-wire dimmer switches is fine.
Note that the first one to switch on will control the brightness. i.e., The one with the brightest setting will win. This is due to the way the ...
- 180k
3
votes
Accepted
Question about a point made in Art of Electronics
In any transistor circuit the collector current will only be \$I_B\$ by \$\beta\$ IF whatever it is connected to can supply that much current.
In this case the lamp is rated at .1A at 10V (1W), so, ...
- 47k
3
votes
How do I connect light bulbs to an alternator on a bike?
You have several problems to solve on the way to a viable solution:
The alternator does not begin to regulate it's output until the speed is quite high (1500 rpm or above). So you'll need to ...
- 22k
Only top scored, non community-wiki answers of a minimum length are eligible