1241

Geek Speak / What programming languages come with my PC, or how can I download one?

« on: 25/01/2010 19:49:53 »

Or run Dosbox, and run win 3.11 on that - 16 colors and crashes too

I use it to play old games from when computers were just starting to become common.

Who remembers Prestel and our variant Beltel - I found I still have a 120/300 baud modem around.

1242

Technology / How is an energy-saving light bulb more efficient?

« on: 23/01/2010 06:44:48 »

The basic question asked was to lamp efficiency. Generally incandescent lamps are very good generators of heat, and poor at producing visible light. Halogen lamps run hotter, and more of the input power is produced as visible light. CFL and LED light sources generate light by using energy level differences in excited electron bands, and produce very little output in the form of heat, thus resulting in the assertion that they are more efficient at producing visible light.

Yes - the efficiency of the device is important, but we should not ignore the fact that it can have an effect on the efficiency of the total system, otherwise we could end up robbing Peter to pay Paul. That was the point that Dave raised.

For example, switched-mode power supplies are common these days. Virtually every computer on the planet uses them because they are very "efficient" (they don't generate a lot of waste heat). However, because the current demand they impose on the power distribution system is very nonlinear with respect to voltage, they can cause a lot of energy to be dissipated in the power distribution system, so, perhaps they are not so efficient after all.

Initially SMPS were very poor with regards to power factor. Your first SMPS was the television set, the worst example was the Phillips G11, which drew DC current from the mains as an 11A pulse every second cycle. This caused a few substations to fail due to core saturation, and started a trend towards a unity power factor. The latest SMPS incorporate PFC to give a near unity power factor, and this active approach actually improves the efficiency by reducing heat losses internally. This is only effective above around 50W, so small units just use a resistor to reduce the current pulse on the input at the expense of a slightly worse efficiency.

The power drawn by electronics is strangely in phase with the voltage, unlike the coil, but is responsible for creating harmonics on the supply, and this causes problems for transmission and distribution, as this causes heating in lines, transformers and power factor correctors. The generation side has to provide Apparent power, not True power, as the load on the generator is only determined by the current output, nothing else. The individual plants switch in and are run up to full load current, and are kept there as the control loops that run them do not respond well to load swings, having time constants in minutes due to large rotating masses. Per se they have a unity power factor, as they are the source, but they supply VA, even though the customer is billed in Watts, with a penalty if the power factor drops below 0.7.

1243

Chemistry / Does beer have a lower freezing temperature than water?

« on: 21/01/2010 19:17:06 »

Certain beers are advertised as " Ice filtered" by being passed though a slush during production. Don't drink beer myself, but like brewers yeast, especially fresh from the drier in flake form.

1244

Technology / How is an energy-saving light bulb more efficient?

« on: 21/01/2010 19:14:35 »

The basic question asked was to lamp efficiency. Generally incandescent lamps are very good generators of heat, and poor at producing visible light. Halogen lamps run hotter, and more of the input power is produced as visible light. CFL and LED light sources generate light by using energy level differences in excited electron bands, and produce very little output in the form of heat, thus resulting in the assertion that they are more efficient at producing visible light.

1245

General Science / Do halogen bulbs need cooling?

« on: 21/01/2010 19:10:22 »

Although the lamp operates at high temperature, it will require cooling to operate properly. Almost all high power projector lamps are forced air cooled, and the manufacturer generally has the specifications for the airflow, direction and other info. Failing to do this will result in a very short lamp life, or the lamp melting or exploding during operation.

1246

Chemistry / What metals other than aluminium can be reacted with water to produce hydrogen?

« on: 20/01/2010 17:07:11 »

Using the hot exhaust to provide power via a turbine would be a better use, and use the leftover power to provide steam to add to the inlet. Google steam cycle for more info, although the steam has a bad tendency to cause cylinder bore wear.

1247

Technology / Can you get coloured compact fluorescent light-bulbs (CFLs)?

« on: 19/01/2010 18:54:31 »

Your "White" CFL lamp uses a combination of different rare earth oxides ( which are almost invariably a greyish white colour when viewed normally)  in a thin film on the inside of a glass tube. The UV light provided by the mercury vapour discharge inside the tube excites the phosphors to provide various colours of light, and this mixed colours is perceived by you as "white" light.

To make colours you merely vary the proportions of the oxides, and use a coloured glass to enhance the output in specific colours. A naked mercury vapour discharge is almost entirely in the UV wavelengths for a low pressure, and has a green light at medium pressure.

Strange that the mercury vapour lamps are being phased out " because they contains mercury", whilst the replacement lamps contain mercury still, as well as metals that are a lot more toxic, and have a lot shorter lifetime. Tossing a mature technology, with a proven 30 plus year lifetime on the lamps, for a replacement that invariably fails within 3 years, often explosively, is not a very good idea unless you are in the supply business.

1248

Chemistry / how far is the gravitational force of earth effective?

« on: 18/01/2010 17:54:48 »

It has an effect on our neighbouring galaxies, but it is a very small effect at that distance. In essence it has an effect thoughout the visible universe, although the effect will be really hard to measure, mixed in amongst all the forces from other bodies forming the visible universe.

1249

Technology / Re: Is It Possible To Heat Up Airport Runways ?

« on: 07/01/2010 17:15:09 »

Black tarred runways, and concrete ones too, store heat and can melt the thin initial layers of snow.

To clear the runway of snow will need a lot of power, enough to melt 1km of ice that is 20m wide per runway. That sort of heater is a little bit bigger than the kettle or toaster, and would probably bring down the local grid when it is turned on.

Snow plows and salt spreaders will be more appropriate, although no airline will want to land on a runway coated with a lovely corrosive salt layer - planes cost a little bit more than a Fiesta, or even a Bugatti, and salt corrodes alloy rather rapidly. The last thing you want is a panel thinking it is made of "House Brand" foil when it is all that separates you from Sir Isaac Newton's apple.

As to the costs of keeping dedicated equipment, almost all airports have at least one front end loader, for general use and such, which can be used as a snow plough for those airports without dedicated snow clearing equipment. A bigger issue is that the aircraft themselves will require de-icing before takeoff, which does need specialist machinery, chemicals and trained staff ( Most important) so that a layer of ice does not spoil the flight capacity of the plane.

1250

General Science / Re: Does a moving train stop momentarily when it hits a bee?

« on: 04/01/2010 08:25:24 »

Not really, the elastic deformation experienced by the small area of the train that experiences the force of the bee impact, plus the larger plastic deformation that the bee undergoes, ensures the rest of the train does not experience any force at all. If the bee was truly incompressible, along with the train, then you would have a very easy form of nuclear fusion, and a very ablated train after a few minutes.

I know of one train driver that had the experience of hitting a lot of bee equivalents ( around a dozen bins filled with gravel, an attempt to derail the train) and, aside from a loud bang from the impact of hitting them, nothing happened aside from the flat steel bins wrapped around the bumper. The same with the cars and trucks he hit on unguarded level crossings. Of course all train drivers can tell about the very large "bees" that wander onto the tracks at times, and the train has no steering ability or short stopping time, just a loud horn to warn with. Train always wins. Always. Gloves and a big galvanised bin are pretty much standard equipment.

1251

Technology / Why Does Wifeys Car Engine Get Flooded ?

« on: 24/12/2009 16:23:08 »

If left for a few hours most of the fuel will vaporise, if the ambient temperature is high enough. This problem is worsened on older vehicles in that the injectors can leak with wear and time, and flood the cylinder with a lot of fuel, that stays a liquid as there is too much, preventing starting. There is enough pressure in the fuel line to flood any cylinder so that it will be very hard to start, and can be dangerous to your catalytic converter by flooding it with unburnt fuel, which it will burn very rapidly on the next start, either overheating and melting, or setting fire to grass under the vehicle in worst case.

As to the lubrication, synthetic oils are lower viscosity, but they are still washed off the cylinder walls by fuel. The main reason for using them is to lower internal friction in the engine, and to enable tolerances to be made smaller and running speeds higher without metal on metal contact. These oils still depend on a pump to get the pressure up, and it still takes some time for the pressure to get the flow to full levels, especially in the head and the crankshaft, which are at the ends of a long oil flow path, restricted by a oil filter along the way that has to fill up first.

1252

Question of the Week / QotW - 10.01.10 - How do you measure carbon dioxide emissions?

« on: 24/12/2009 16:09:46 »

For most I would hazard that they measure how much oil, gas and other fossil fuel they import or consume, and assume it is solid carbon mass for the most case.

Or they do a ginormous thumb suck, based on other similar populations and incomes.

1253

Physiology & Medicine / How biocompatible are nanowires in the brain?

« on: 24/12/2009 16:06:26 »

Particles around thate size ( asbestos) have the potential to be harmful over time.

1254

Physics, Astronomy & Cosmology / Why can Hubble see distant galaxies, but not nearby planets?

« on: 22/12/2009 17:05:11 »

Hubble can image the earth to a resolution of around 30m. There are better spy satellites, capable of better than that on a good day, but they do not have Hubble's low light performance, or the wide range of spectra available. Kind of like using a F1 car to go to the corner shop to buy a loaf of bread, you can do it, but it is not the best. Hubble is best for long exposures to image really big objects in various wavelengths, giving better detail than ground based instruments because of no distortion on the long imaging time.

1255

Geek Speak / What programming languages come with my PC, or how can I download one?

« on: 22/12/2009 16:59:33 »

Python is also available for free, at www.python.org for you to use. Comes with a command line, and plenty of examples and tutorials on the internet.

1256

Physics, Astronomy & Cosmology / Why does AM (medium wave - MW) radio reception worsen or deteriorate at night?

« on: 20/12/2009 15:49:41 »

AM and FM are both forms of modulation, basically the method how information is carried via a radio wave. The most basic is via morse code ( the beeping you hear on LW, MW and SW radios) where the information is carried by switching the transmitter on and off. If you vary the power output, keeping to a fixed unvarying center frequency, and do it in sympathy with the desired signal ( speech or music) and at the receiving end you feed the information about the changing power to a speaker, you get the classic AM receiver. Any interference on the same frequency will either add or subtract from what is the instantaneous power received, giving rise to the noise and static heard on the radio.

FM radio works by transmitting at a constant power output, and transferring the information by varying the frequency of the transmitter around a centre frequency. At the receiver the signal is limited ( so as to remove any changes due to varying level due to noise and changing signal levels due to moving or local interference) and then the change in frequency is recovered to form the original signal. As most of the noise is AM this reduces it considerably without affecting sound quality.

The major reason that FM is on higher frequencies is that the bandwidth required for a FM signal is a lot larger than that required for AM, which has channel spacings of either 9 or 10 kilohertz, depending on the location in the world of the transmitter, between channels to reduce the possibility of interference and around 5 kilohertz bandwidth. Most broadcast FM has a channel spacing of 200 kilohertz, with a typical transmission occupying around 150 kilohertz of that. That is why most FM broadcasts are on high frequencies above 79MHz. You can operate a FM transmitter on the AM bands, using various methods that reduce the bandwidth required, although these severely limit the quality, and require a more complex receiver to decode them. FM has the ability to offer better sound quality, and stereo sound as well, with relatively simple receivers. To do the same on AM requires more bandwidth than most operators will license, and loses compatibility with the current base of listeners equipment.

AM radio can, depending on conditions and time of day, be heard worldwide relatively easily. FM transmissions can do the same, but tend to be hard to receive due to the reuse of broadcast frequencies by many transmitters world wide. TV signals from New Zealand are often received in the UK for short periods, as those who are older and who remember 405 line TV can attest to.

1257

Chemistry / Which chemical dissolves the color on magazine pages?

« on: 16/12/2009 19:09:49 »

Do  a colour photocopy with a laser printer and transfer the image by using a hot dry iron to melt the toner onto the receptor surface. Use a overhead transparency film for better results, or for the best use a t shirt transfer sheet that you soak in water to release, it has a soluble film on one side that releases the toner.

If you use inkjet printers then a misting with water or methanol/ethanol will transfer well, albeit with some image bleed. Try the steam iron in this case.

The big issue with current magazine inks is that they are now almost all rubber/water based, and are heat/UV cured during the print process to stop the ink from transferring to your hands during handling. This makes then pretty much insensitive to solvents, as they have changed chemically due to the heat or UV curing.

1258

Question of the Week / QotW - 09.12.13 - What would happen if you Tasered an elephant?

« on: 11/12/2009 19:06:56 »

I know of a Rhino that accidentally walked though an electric fence ( not the common cattle kind, but one designed to kill you, not just warn) and was none the worse for it, aside from a very much worsened mood from the shock. He was herded out and made another similar sized hole on the way out.

The elephants learned how to handle the fencing, they dropped two trees across a section to flatten it and walked across the flat wire. When the trees were cleared from near the fence they simply brought them in from the scrubland to flatten it. They were attracted by the green vegetation and lush grass inside.

Elephants have thick skin, but it is very sensitive, especially the feet and trunk. Tasering an elephant is likely the second last thing that you will ever do, as the very annoyed elephant will almost invariably catch you and trample you into a bloody smear on the ground in short order.

1259

Technology / What objects should you not put in the microwave?

« on: 11/12/2009 18:21:13 »

There is one light source intended for use in a microwave - the sulfur lamp. It is powered by a slightly modified microwave oven ( mostly extra cooling as it will run essentially 24 hours a day in most cases) and is one light source where the lamp will almost invariably outlast the power source ( along with induction lamps). It heats the small amount of solid sulfur sealed inside a glass sphere until it ionises and emits a brilliant white light. Used in the Smithsonian museum to light the main hall via a light pipe to distribute the light evenly.

Generally microwave only food if you intend to use the oven again to ever heat edibles, as it is near impossible to ensure that any harmful vapour or particles emitted by doing other experiments are removed from the interior and the cooling path.

1260

Chemistry / What happens if you chew explosive material?

« on: 11/12/2009 18:20:29 »

Explosives range in sensitivity, from stuff that literally will explode if exposed to light, to explosives that will not detonate even if hit with a hammer. Most commercial explosives fall in the latter category, and many are very safe to handle until they are fused. The fuses are generally a much more sensitive item, using rather noxious chemicals that are sensitive to shock, temperature, moisture, chemicals and pressure. This is needed to get them to initiate the main explosive they are inserted into.

From the little I read, this chemist made some relatively sensitive explosive, and the combination of this, and probably the silver mercury amalgam in his fillings combined with the jaw pressure, caused it to detonate. Not a good day for him at all.

In the world there are still daily discoveries of old war era ordinance, most giving concern due to the age of the triggers making them very sensitive to disturbance, the main charge still being dangerously effective after all this time, especially as you do not know why it initially failed to detonate.