studiot

Thank you each for your contributions. We have regulations coming out of our ears in the UK They are just not enforced. Worse it seems in this case they were not even checked for compliance with the regulations. Even worse the perpetrators appear to have sought to hide their wrongdoing by 'gagging' clauses in exchange for meagre compensation, once found out. That is the result of a 'seller's market' I put this in Politics because I think that includes the science of (science ha ha) economics. One thing 'free market economics ' assumes is that the seller and buyer have equal bargaining power which is almost never the case. So the politics question here is how far is the balance tilted towards the sellers and is it getting worse?

I mentioned an earlier thread, I thought due to Capiert,about connecting D cells, but I can't find it at the moment. However I did find this. Have a quick look through it and see how the information is presented. (look at the many pictures)

No, one coil will not increase (or decrease) the voltage. It can, however lead to switching transients which can be of quite high voltage. I'm sorry but you have lost all credibility with me, as well as wasting a substantial amount of my time. In particular you concealed the fact that there was some connection to a coil but have not told us how this coil was connected. You also initially omitted to mention the cabinet though I don't see how the absence or presence of a cabinet can affect the activity of the circuit. So what else are you not telling us ?

https://www.bbc.co.uk/news/business-46454844 Large scale shoddy materials used by large (reputable ?) building firms who tried to impose gagging orders in exchange for compensation. They could certainly do with some scientific emthod type (independent?) inspection and verification.

+1

Yes you are right, I did. But that was a hypothetical situation that you might have misread the meter (it happens) and your reaffirmation without proof has not increased confidence in your supplied information. Particularly in view of these two statements followed by this These statements contradict each other, Are you trying to trick us? So you can't say how long the D cells were supplying 40 mA for. But you didn't mention this at the outset? And now you expect us to believe that D cells which are Pull the other one.

Why are you saying this? No one quoted 75 mA. How do you know? If you were there watching, why did you not take intermediate readings? Also have you repeated the test and found the same result? No you haven't. You have left too many questions unanswered, both from myself and others for verification. What is the type number of your LED? Do you have any photographs of the setup and the meter readings? Not long back there was a thread about parallel/series connection of batteries. In order to help I posted several photos and closeups of the meters in different configurations. Perhaps someone will remember this thread.

I seem to remember that many LEDs have built in limiting resistors.

Good, you are talking about something scientific. Now if you would be so kind as to link your comments to the thread topic rather than sneering at the efforts of others (teachers of elementary science in this instance) we could move towards a proper discussion. You never know, if you tried hard enough you might actually be able to support your case with evidence. By the way, Hooke's Law was a simple something that came to mind as an example. I did imply you could choose your own. Your scenario was not the one I had in mind, schoolboys are much more likely to measure tension or perhaps flexure, since compression experiments are much more difficult to handle and control and potentially more dangerous.

Yes this has merit, though it is not 'totally the wrong picture'. That would be too strong. We call the is difference between local and global phenomena. I think there is a language barrier here. Try to post a small bit at a time so we can agree what you are saying.

Yes indeed it is. But like most things in this world, It needs to be taken in context. And the context here is that ScienceForums is fundamentally a Scientific website. So subjects such as General Philosophy, Religion etc need to be discussed from the point of view of of their relation to / interaction with Science and from a scientific perspective. Obviously purely philosophical material (in this case) will be also introduced but its link to Science needs to be there. I would venture that a 'compare and contrast' type contribution to the discussion is perfectly legitimate. Indeed I have seen a professional barrister member here do exactly that comparing the legal and scientific interpretations of evidence and proof. There is one section of the forum where any subject, including non scientific ones, may be freely discussed. That is called the Lounge.

Yes it's possible that overcurrent might have damaged the LED so that it has become a low value 75 ohm resistor. +1 But would it still be giving off light?

Can we please discuss Scientific evidence and proofs, not legal or spiritual (in the whisky sense) or any other sense.? For example take a typical schoolboy experiment to 'proove' Hooke's Law where he does some measurements and draws a graph and then says I have obtained a straight line through the origin so I have prooved Hooke's Law. Has he?

That is not what I said, but I agree that I have been very brief and QM is a huge subject. Take a look at these four pages from Atkins book and see how you get on. At the end of page 44 and into page 45 he makes the important point that the quantisation arises as a result of the boundary conditions imposed on a classical equation. As to the issue of 'operators' Heisenbeg's Principle arises from the same inequality as Cauchy-Schwarz or the triangle inequality when considering the product of two distributed (spread out ) properties.

I wish I could remember why I posted that. I know I had a reason at the time.

No, it is not supposed to happen, the current (and light emitted) should reduce as the batteries drain. You haven't reported what happened to the light output from the LED? Possible explanations: You misread which scale you were using and it was actually 75mA initially. Did you have to change scale to go from 7.5 to 40? The batteries were initially very cold and their output voltage was low. They then gradually and warmed up through ohmic heating Were there no intermediate readings? 8 hours was a long time between. There was intiially at least one very poor contact which improved with the passage of current.

Here are some conclusions that ere drawn a long time ago (1923). Looking at a 2018 cosmology/relativity text they are still recognisable and current. As far as I can tell we still have not resolved the questions of alternatives, though I would welcome more information.

So our current drilling capability has only taken us 0.2% of the way there. We will have to continue using indirect investigative methods for a long time yet. Until the last few years, we have also been unable to recreate in the laboratory the conditions of pressure and temperature at depth. The diamond anvil has changed all this. https://serc.carleton.edu/NAGTWorkshops/mineralogy/mineral_physics/diamond_anvil.html

I remember learning about this in one of my very first Chemistry lessons at school. Lead has been used since Roman times for making water conduits since it does not rust away like iron as John said. However over time softer water, which is can be slightly acid, slowly attacks even lead taking away small quantities. Lead is a cumulative poison in the human body so this is clearly undesirable and even small quantities are undesirable and add up over time. As a result, authorities in the UK, and no doubt elsewhere, are required to maintain the supply of potable (drinkable) water within certain limits. This is usually measured by hardness rather than the pH acidity scale (We did an experiment using Clark's Standard Soap Solution) The degree of hardness has other features and implications to as well as acidity so it a wider measure. Please note there should be no lead in brass taps or other fittings. Any lead will be from old fashioned soldered joints. Modern solders are required to be lead free. Note that lead was also used in paints and electrical solder, both of which have/are now being phased out. Does this help?

So do you agree that the Universe includes the space between that atoms, between the planets, between the stars, between the galaxies as well as the atoms, planets stars and galaxies themselves? Bizarre or otherwise it is loose terminology that is preventing proper discussion here about the important comments to be made on dark energy and dark mass. Since we don't know what these are we don't know if there is only one type of dark matter and dark energy or there are many and if so if the contributions are evenly spread or not. This is not an idle discussion; Consider lumped parameters (which is mathematically what dark energy and dark matter are) The mathematical process of 'lumping' depends upon the nature of the interface between the parts and leads to theorems such as Norton's Theorem and Thevenin's Theorem. But these do not alwys hold good. Let us consider further a bloody great circuit comprising millions of transistors with thousands of inputs and outputs. Now let us draw a cut line (interface) across the power supply rails and note there is 'something' on the other side of that cut stabilising the power, equivalent to 10 Farads though we do not know how this is achieved, only that it is and actually many times bigger and heavier than the entire rest of the circuit. Would you say that this lumped capacitance is 98% of the circuit?

One of the important lessons in Critical Thinking is to learn to recognise nonsense when you see it and also to recognise when that nonsense arises because something is poorly defined. 1) The phrase "% of the Universe" is one such phrase. A proper definition would be along the lines of "% of all the XXX in the Universe". But you can't lump "all the XXX with "all the YYY" to calculate a %. That is nonsense. 2) Most authorities hold that by far the largest part of the Universe is unoccupied space. Are you excluding that? Shame on Nasa for such populist nonsense.

Solved Actually it is not the number lock but following all you guys' helpful hints was brilliant. This laptop has a 'pad'lock in addition to the number lock as well as a little light for each. The padlock toggle is fn + f10. And yes it also has miniscule blue letters on the relevant key edges. So thanks and +1 all round for steering me in the right direction.

Thanks guys, I will try out your ideas and report back. A correction, the keyboard has a normal line of numberers above the querty line. It just has no separate number pad. Sorry for mixing up pad and board. Curioser and curioser. I tried Sensei's safe mode suggestion. This has 3 users, Studiot, the former Owner and the built in administrator. It is the studiot account that is duff, the keyboard operates normally on the other two, both in safe and normal modes. The studiot account misbehaves as shown in both safe and normal modes.

This laptop has no numeric keyboard. It is an Acer Travelmate 4051 LMi. Here is a sceenshot of typing the top letter line with both the laptop and an external usb keyboard connected. The usb kb. is OK

Actually, you are right. I did miss your point, having read it, again. Sorry about that. Do you have links for this claim, of yours? I would be very interested in it. Sure, though most of my material lies in published and vetted hard copy, not ephemeral links. First and foremost, when we calculate a 'quantum' of something it is a something with a classical definition. Most usually, that something is Energy. But not any old energy. Quantum theory does not restrict 'any old energy' to specific values, say 1 unit or 2 units , but never 1.5 or 1.3 or 1.86742 units. What is does do is make such a restriction for a specific system. And of course, the energy is the same ML2T-2 quantity that appears in 'classical' theory. We still have to multiply a classical force by a classical distance to obtain it. So when we analyse the quantum mechanics of vibration of the carbon dioxide molecule to obtain its infra red spectrum we still consider little balls on springs. The point is that the solutions have special characteristics at certain frequencies, leading to 'quantisation' of response. We can even introduce Relativity and calculate a relativistic Doppler shift due to the oscillation of the little balls about a mean centre of mass. Again consider Boltzman, Statistical Mechanics, the Partition theorem and classical Thermodynamics. They all offer analysis of a system in standard states, with fixed transition energies in terms of the distribution of the energy carriers in the system throughout those states. Does that sound at all like QM to you?