To nuke or not to nuke

[Master Splinter]

Change in direction of the plate is due to the interaction of the pattern on the plate and the 50 Hertz flicker of the light.

Stroboscopic effect - Wikipedia, the free encyclopedia

[Sturdee]

. At this early stage, my obsession is centred around the fact that the turntables of all microwaves seem to rotate exactly a whole number of revs in one minute so that the handle of the cup is facing you when it finishes if you press a whole number of minutes........................... Tomorrow I must get a life.

The latest type of microwave doesn't have a turntable, you just put the cup in it and it stays in position. So upgrade and it will help you to get a life.


Peter.

[Bushmiller]

Change in direction of the plate is due to the interaction of the pattern on the plate and the 50 Hertz flicker of the light.

Stroboscopic effect - Wikipedia, the free encyclopedia

MS

I was about to do the smart **se thing and say that this obviously doesn't apply in countries that generate at 60Hz, but of course it does, although at a slightly higher speed.

Thanks to physicists MS and Ian, potter TL and all the other miscreants for an entertaining way to learn.

Regards
Paul

[Ian Smith]

MS

although at a slightly higher speed.

and in the opposite direction in the northern hemisphere

[AlexS]

The serious bit about the stroboscopic effect is that rotating objects such as lathes & router cutters can appear stationary under fluoro lights. Don't know if I'm correct in thinking that incandescent light used to be required in industrial situations.

[Ian Smith]

I was concious of the effect when I put lights in my shed, but no matter how I tried I could not reproduce the effect on routers, drills, circular saws and other rotating objects. I put them in good lighting (fluro spotties) and ran them through their speed ranges but nothing was evident.

I suspect that not only does the light need to be quite strong and but there also needs to be good contrast between the teeth, blades etc and the background to produce the effect which is why the little discs in the centre of turntables work as they have black and white segements and I supose the internal lighting is strong enough.

A mate of mine used to run a large industrial fabricating establishment and he was very aware of it as an OH&S issue

Ian

[BobL]

I was concious of the effect when I put lights in my shed, but no matter how I tried I could not reproduce the effect on routers, drills, circular saws and other rotating objects. I put them in good lighting (fluro spotties) and ran them through their speed ranges but nothing was evident.

I suspect that not only does the light need to be quite strong and but there also needs to be good contrast between the teeth, blades etc and the background to produce the effect which is why the little discs in the centre of turntables work as they have black and white segements and I supose the internal lighting is strong enough.

One thing that people forget is that there needs to be very tight synchronization between the 50 Hz of the lighting and a low multiple integer of the RPM of the rotation but there are not many small motors that synch with the 50Hz. For example 50Hz should equate to 3000 rpm for a two pole motor but a more likely RPM is ~2800 rpm

In addition, if there is any illumination by refection or other lights the effect is greatly diminished.

[rhancock]

I'm not mechanically talented, unless a push bike counts, so I may be barking up the wrong tree, but isn't a timing light using this phenomena?

[Ian Smith]

Yes

[Master Splinter]

And this is just a freaky example of the effect....

[ame=http://www.youtube.com/watch?v=LVwmtwZLG88]curious stroboscopic effect - YouTube[/ame]

[AlexS]

I've seen it demonstrated with an adjustable strobe light, and also seen it as a router slowed down under fluoros, but you wouldn't have mistaken that for one standing still.

[mic-d]

And this is just a freaky example of the effect....

curious stroboscopic effect - YouTube

In addition to a stroboscopic effect, that particular effect is due to the rolling shutter effect which is also the reason the photo finish photos are distorted.

[Avery]

I have a turntable for playing vinyl records (remember?) that has a series of little checker patterns around the edge and a speed adjusting knob. You put the platter on, place the tone arm on the record and then adjust the speed until the pattern appears to stand still, and there you go , precisely 331/3 RPM. Completely useless really.

[damian]

The Straight Dope: How come the wheels of a moving car appear to rotate backward sometimes?

Far more reliable source than wikipedia...

[bsrlee]

Melamine based eating ware is NOT microwave safe. It seems that water (or something) is caught in its structure & is heated preferentially by the microwave - I've seen soup in contact with a melamine bowl boiling around the edge while the middle of the soup, away from the plastic but still exposed, was cool to the touch.