1) Flicker: does the LED's high-speed flicker play a role in damage to the eye? (Here's an LED viewed in slow motion: https://www.youtube.com/watch?v=3wdljou1M8Q)
2) Spectrum: LEDs can have very uneven spectrums with spikes at particular frequencies (particularly in applications like street lamps that don't use phosphors). This is something an eye in nature would never experience.
Here's a great video showing LEDs strobing compared to other bulb types: https://youtu.be/1IDf16R_eJ0?t=13s
In the living room or especially the bedroom and bathroom, I prefer dimmer lighting with less blue spectrum. My 29W halogen incandescent on the night table doesn't exactly burn through a lot of electricity and has the most pleasing light in my eyes. Until there's a LED that can perfectly match that, I'll stick with that until these bulbs get banned, too.
Or, do what I did. Just make the rectifier directly out of LEDs itself - https://www.youtube.com/watch?v=jDnCHyF7o5U And from there you can power your devices with the leftover DC power.
LEDs are seriously far more robust than they were a decade ago.
That's not PWM in the video. That's raw mains frequency.
Here's one directly on the mains power. NO CONTROL CIRCUITRY.
Sodium lamps are much less objectionable because their spectral spikes are at much longer wavelength.
The only sodium lamps I'm familiar with are high pressure sodium, which emit a garrish orange hue.
https://www.youtube.com/watch?v=l6bTSJVLCVI - I used to build fully-functional hydroponics buildings from the foundation-up. Electrical included.
Ground is for safety in AC, when there is a short the ground should take the current away resulting in power loss through the earth that in turn makes the breaker flip. Without grounding the wire that is exposed and touching something will (depending on material etc.) not transfer any current because of too high resistance, then as you touch it it will shock you and then the breaker will go off.
(A loss power breaker, not a draw power breaker)
Perhaps you mean the neutral?
Same way you complete any other ground - since ground and neutral are literally on the same leg (go look at any installation. You've got TWO wires coming in at the mains, ungrounded.)
So, tell me, how do you ground those ungrounded 240/277V wires??
You don't. Both of them ARE the natural ground dependent upon whether you're at the peak or trough of the waveform. That's kinda how AC works.
Where I am from we have installations differently.
phase and neutral come in the box, they go through a loss breaker(RCD) and then split up in to multiple breakers.
Then those wires go to the socket.
Then near the box there is a metal rod in the ground with a wire going to the box, this wire connects to the ground wires coming from sockets.
The ground wire, is not connected to anything but things that are not supposed to have any power flowing through.
Yes Neutral is grounded (outside my house, on the main)
But when we say we ground things we mean the third connection.
Sorry, didn't know it was so different over there.
edit: Saw the correct name for the "loss breaker" in other post, it is RCD :)
edit: Question, what happens if you hold the neutral to the ground wire there?
Forgive my ignorance, I'm no electrical expert, but did you just say that the ground wire is connected to the neutral somewhere in the circuit? Or did I misunderstand you?
EDIT: That "always" is assuming the house is modern wiring and not older-style two-prong wiring for the wall outlets. Those systems were just main and neutral at the box and controlled by a fusible link.
If I'm understanding you correctly, in the US the ground wire is functionally identical to the neutral due to the bonding. Therefore (this is my own deduction and I'd appreciate being corrected if I'm wrong) you could, in theory, invert the ground and neutral wires in the plug of an electrical appliance and there would be no change in the behaviour or safety of the appliance?
Generally, no. I've seen backwards wiring jobs cause 48-80VAC to run through the casing of microwaves (they usually use the casing as a floating ground.) Any wiring inversion will usually cause some issue somewhere.