studiot

Have you studied electric fields? The relationship between B and H is very similar to the relationship between E and D. In many situations one is a constant times the other but in non-isotropic media they may point in different directions (they are all vectors). If you let me know whether you understand about E and D I will explain further.

I quite like the practice of heading chapters with a pithy and perhaps witty quotation. One of my favorites is Another good one is

Two thoughts about the replies here. The OP is talking about A levels, which are intended for 16 - 18 year olds. Many of the replies are about maths for a much younger age group. Several have offered problem solving. I like problem solving and thinking for myself, but many do not. They prefer to be told what to do. What do you think they would make of being forced to problem solve? Of course there is the question "Is the mantra maths, maths and more maths is good education for everyone" actually true? Or are we boring many with subject matter they don't appreciate and will never need?

In 1967 the A level exam was a privilege. Approximately 15% of pupils in any one year took A levels at that time. I don't have reliable data on the % of these who took maths, but it was one of about 15 popular subjects, but by no means the most popular so the % would have been around 1%. About 3% of pupils in those days went on to become students at University.

Welcome Martin, but I completely failed to understand the point of your OP. No one is forced to take any A level subject, let alone A level Maths. It is elective and what's more the number of A levels a student can take during 6th form is limited. So why did you take A level Maths?

Do we not already have an alternative and dare I say better classification. Subjective and Objective? Properties including gravity would fall into the subjective category. The great steop forward due to Einstein was to show that many so called properties depend upin the observer and no one observer's view is preferable. Maths would fall into the objective category, but Russell, Godel and others showed that there are limits to this. Maths is certainly not 'absolute', partly as imatfaal showed and partly due to Godels theorems.

Yes we have evidence that energy can do but also evidence that it can come in any value, depending upon circumstances. Does this affect you question? Professor Majid of London University edited a recent Cambridge University book on this very subject, with many famous contributors. On Space and Time https://www.amazon.co.uk/d/Books/Space-Time-Canto-Classics-Shahn-Majid/1107641683

To address the question part of your OP, here is a paraphrasing of a long section by William Berkson on this very subject. Up until Einstein physical substances (bodies) were regarded as having the following characteristics. 1) Definite, unique location in space and time. 2) Identifiable properties, uniquely specifiable that are always present with the body. Generally these properties are conserved in during changes in space and/or time. The notion of substance was incorporated into the scientific approach; scientific development was aimed at deducing all laws in terms of the motion of the substance. These Laws were regarded as the basic laws of the Universe. Einstein denied the existence of physical substance in this role or meaning. He thought that we cannot uniquely assign to any portion of matter or the field the properties that were traditionally regarded as substantial. In different frames they will have different values, according to the Lorenz transformations and Einstein asserted that we cannot regard any of these different values as the real one. All are equally real. For instance the mass of an object cannot be uniquely specified as in different frames an object will 'have' different masses and none can be singled out as the real mass. Similarly the same applies to the space occupied by that body; the dimensions of a body are different in different frames. The times associated with different parts of an extensive body will also be different so we cannot even view extension as a substantial property. Furthermore these arguments also apply to any aether we propose, dispelling the validy of an aether. Properties formerly and subsequently regarded as insubstantial such as the speed of light are the same in all coordinate systems. I would recommend Berkson's book as offering some clear and well researched and thought out insights, both philosophical and scientific, although there is some wading through to be done as well. There are many extracts from published writings, papers and lectures of Faraday, Maxwell, Lorenz, Einstein and a host of others. Fields of force A development of a World View from Faraday to Einstein. (actually he goes a bit back before Faraday and forward beyond Einstein)

We have had several students reports heavy Easter workloads It's all a dastardly plot by the establishment to keep them from enjoying that wonderful weather we are currently having. Rest assured there are plenty of competent responders here for your field. It's good to try to develop a relationship as folks are more willing to help when they know you a bit. A tip Wherever you go for help and advice (the web, college, books...) always establish the engineering conventions in use at the outset. There are a number of contradictory conventions so find out quickly to avoid cross purposes. There used to be a non profit teaching site and forum called allaboutcircuits.com They were very friendly and I had many good conversations there. But they have been taken over by commercial interests so there is always a hidden agenda there these days advertising certain products. About half of the excellent specialists left when the takeover happened, and I don't visit often now myself.

You really need to explain more about your question. Are you studying curve fitting? Do you have any expectation as to the form of the curve, I see that it goes up and then goes down again? Have you any thoughts on the curvature or the endpoints? When we try to fit a curve to data points, we have to decide in advance what is the maximum power of a collocating polynomial we are looking for and also whether we want this polynomial to match curvature as well as data values. Sometimes we use special curves such as splines to fit at the ends because we can't calculate the curvature at the endpoints as we don't know what the actual data is beyond our endpoints. A polynomial may fit quite well over the range but go wildly astray outside this. This is especially true of high order polynomials. Achieving curvature fit as well as best fit at the data points means that the data at some points has to be employed to obtain curvatures. So there is always a trade off between the use of the data points to achieve a closer fit at the data points and to get the right curvature. Of course there is also the statistical approach. That is to calculate the best average fit for a specific nominated curve. So which one is it to be here?

Have you heard of volumetric alarms? http://www.foxspyoutlet.com/security-equipment/smart-sensor-volumetric-alarm/

There is no such thing as absolute time. So there is no such thing as absolute 'running' of a clock. This is another way of saying or a consequence of the fact that every observer will see any clock running differently. You will not progress until you accept this basic fact.

The outward and return journeys cannot be symmetrical. Yes the travelling clock appears to run more slowly to the stay-at-home clock on both legs, but, On the outward leg travel is away from the base so light (or any other) signals take longer and longer to traverse the expanding distance between the two. On the return leg it is the other way round the separating distance is diminishing so signals arrive more and more quickly. This fact has nothing to do with Einstinian relativity, but must be factored in to any analysis.

Hello Mondie, it is a long time since we shared a thread. Anyway I am somewhat confused as to what you are seeking. Are you saying you understand the electrical/electronic engineering aspect from a point of view of connecting appropriate devices together, but not how the devices work and would like to understand how they work. Or do you need help with auto electrics as well? The main difference between auto electricity and domestic wiring is that domestic wiring is AC or alternating whilst autos run on DC or Direct current. It is true that modern autos use an alternating generator (alternator) rather than a direct generator (dynamo) but this is converted in a module mounted on or within the alternator. But yes the voltage is lower and the current higher for the same power requirement, but not otherwise. Modern vehicles also have a plethora of sensors (transducers) which measure/monitor all sorts of activity in the vehicle its mechanics and surroundings. Do you wish to know how these work, for example the lambda sensor in the cat converter? This is the province of control engineering. So tell us a bit more about your intended project so we can offer focused help and references.

The use of extremal quantifiers or qualifiers such as; none, all, never, always, perfect etc often leads to a paradox or other difficulty. Some examples I always lie. Every statement I make is false. Every statement containing extremals as noted can be disproved. I just wondered if you really meant to include something like these which work just as well with a finite set as an infinite one. For instance 'always' is a sort of infinity, but not for me since I have a finite life and can only make a finite number of statements in it. Otherwise If you really meant that all paradoxes are based on infinity there have already been plenty of counterexamples that disprove the claim.

http://www.bbc.co.uk/news/health-39518580 This seems to be a highly significant breakthrough, if verified. Further references welcome.

Strange, see my post#10 ref

I posted a comments on the twins in this recent thread, now closed. No one seems to have taken up on as a way of avoiding the acceleration question. I don't know if I may refer directly to the thread but the post was #109.

Do you really mean 'infinity' or perhaps 'somehow all inclusive or all exclusive within the context of the proposition' Rule1) There are no rules. Buy Johnston's biodegradable, indestructible socks. A self-effacing process.

This whole question is rather puzzling. It is puzzling because the material is not taught until a specialised course in electronic engineering at University or College. It is not even always taught in similar level electrical engineering course. Previously you struggled with some much simpler problems that might have been offered in Physics at A level in secondary education. You have said that you are preparing for imminent exams, so what are you studying? We want to help but it would be really useful to know where you are coming from. Back to the question. You have a circuit with 5 elements, three of which do not obey Ohm's law and two of which do. In the circles you have a fixed current source of 12A and a fixed voltage source of 36V. You seem to have added 12 amps to 36 volts at some stage in your figuring? In the diamond you have a current controlled current source of value 2xi where xi is a circuit variable from somewhere else in the circuit. Unfortunately you have not told us what the question says about xi There are 6 loops in the arrangement, but not all of them represent independent equations. I have said to you before you should redraw a circuit into the most convenient form (teachers like to obfuscate to exercise the mind) and that you should get used to recognising small series and parallel arrangements. I have done this below, the second diagram shows your circuit in standard form. Note the current sources are working in opposing directions.

Well yes I did find some pills but I can't remember what I'm supposed to do with them, perhaps a glass of your instant water might be useful. Don't worry about the debt, phi, I've just made an amazing discovery - negative numbers. I will pay you -1000% interest so If I could just remember my bank account number I could tell you where to pay it in.

I can't for the life of me see how what I said could have given you that impression, but I am sorry if it misled you. Read inertial frame for coordinate system if you will. Personally I don't like the term (inertial) frame as it means something quite different to me, but it is well used.

Oh drat I remember now it was the memory pills I was looking for.

When you have helped JC (+1) perhaps you can help find that £50,000 note I lost last week.

Points are observer dependent, ie they depend on the coordinate system. Events are agreed by all eg the twins meet again or they don't. But different observers will differ as to the point at which this happens just as with my cigar example the observers differ as to the point when the cigar burns out. Another 'point' about points and events. We are treating all bodies as 'point particles' when discussing events concerning them. This may or may not be appropriate, just as in classical mechanics. @steveupson. I introduced a particular example to answer someone else's question about whether we can observe length or time contraction or not, not to discuss your pet direction obsession.