Doubt Definition and 580 Threads

Can anyone please tell me the function of the IC Max232 in a microcontroller board. Is it only necessary for serial programming. If I'm programming my board via parallel port, then do I require this IC? Why? What is TXD and RXD and what are their functions. Also why so many capacitors?

As far as I know a D0 brane is same as a point particle. If that is true then its presence in string theory would go against the very philosophy on which string theory is based (due to presence of 0-dimensional objects). Is my understanding correct? Also it seems to me that D0-D0 brane...

I was watching 18.02 now and Denis Aurox, the prof. who is lecturing, mentioned that for a force to be conservative, not only was it necessary for its curl = 0 but also that F is defined and differentiable everywhere. He then went on to give the example y<i> + x<j>/x^2 + y ^2 will not be a...

i have written a program to plot dst index values using fortran + pgplot, read the input as formatted input when I'm trying to plot the data points are not plotted correctly. k = 0 do i = isdt, iedt --------------start date to end date do j = 1,24...

I have a basic doubt about the usage pf 82C55. Wanted to know when exactly it is used. Eg: For a keyboard you have to use a 82C55 but for a LCD it is not necessary. So when exactly do we use it??

a charged particle ( say 'q' ) moving with velocity 'V' in a region containing a magnetic field 'B' experiences a force 'F' given by: [FONT="Arial Black"]F = q(VxB) when V = 0, then force = 0 my doubt is, is this velocity relative to the magnetic field ? ( i.e. when the velocity...

This is kind of an odd post. To be honest, I don't really expect to see many responses, but I'm going to post it anyway. Back when I first started getting my degree, I wanted to prove something to myself. I had some self-esteem issues, a bit of an inferiority complex. I just needed to prove...

Consider this situation. A non-rotating wheel is cruising through space such that its velocity vector is at some angle to the wheel plane. (Like when a car slides through ice when the driver turns the steering wheel). When its base touches a surface with friction, it takes a turn and its new...

in Thermodynamics, in a book i have read that during expansion of a gas(system), W(on system by surroundings)=-ve..They have proved it using W=-force(external)*displacement. They are saying as displacement is positive and force is always considered as positive, W=-ve. But, how did they determine...

Coulomb's formula states that the force of attraction between two electrically charged bodies is k(q1*q2/d^2), where k is 9*10^9 Nm^2/C^2. However, I have a doubt regarding this. We know that like charges repel and unlike charges attract. Let us take the case of like charges first. If both q1...

In thermodynamics, we always need to use exact differential relations to find the so called Maxwell relations. For a function of x and y, z=z(x,y) if dz = M(x,y)dx + N(x, y)dy the complete conditon for above equation to be hold is \frac{\partial M}{\partial y} = \frac{\partial...

I have a doubt regarding the proof of Length Contraction. The proof of length contraction formula goes as follows: You choose a frame S (as shown in figure 1), suppose w.r.t. S, AB is moving with velocity v. Length of AB is L in AB frame and L1 in S frame. At t=0, a light pulse (shown with...

Hello, while studying thermodynamics I was wondering why, in a system where the pression is not univocally determined (for example in irreversible trasformations), to measure the total work of the trasformation, we use to consider only the external forces. I mean, this sounds conceptually right...

I just read the chapter in Shankar regarding path integrals (the 8th) I didnt quite get how he deduced that destructive interference in the summation sets in after S/h>pi.(This is the first section itself) I couldn't find reference to such a thing elsewhere.

Doubt in Love's hypothesis... Please help... "Normal to the reference surface of the beam remain normal to it and undergo no change in length during deformation" What does this mean? please help...

If a ball collides elastically with a stick at a point other than its centre of mass, then can we use coefficient of restitution is one or do we have to use initial kinetic energy = final kinetic energy?? If we can't use "coefficient of restitution is one" then why?

Is there any doubt in the scientific community to the theory of emergent properties? I am of the opinion that they surely exist. In fact even today's fundamental particles might be an emergent property of something more fundamental. All of stat mech is a study of emergent properties, not to...

Hey i have a doubt . i have not tried this experiment but i wanted to know what would happen. If we take a tube bending at the end and joining to a 5 km long pipe which is frictionless (assume) and there is no air to offer air resistance . So when i start rolling the ball will it stop or not ...

Hi to all.. I am doing Phd in bioinformatics, having little knowledge abt maths.. I have calculated Phi Psi angles(dihedral angle)between two planes... But the thing is i didnt get proper sign for my result(may be + or -). I used following formulae for calculate the dihedral angle between...

We know x^2 = x*x*x*x... x times If we differentiate both sides with respect to x, we have 2x=1+1+1+... x times i.e. 2x=x i.e 1=2 How is it possible or am i making a mistake? Please helpp!

Homework Statement This is from Advanced Physics by Adams and Allday, section 8, practice exam questions, question 25. An α-source with an activity of 150 kBq is placed in a metal can. A 100 V d.c. source and a 109 Ώ resistor are connected in series to the can and the source. This...

Hi When naming organic compounds, hydrocarbons for example, it's very common to have several radicals of the same group attached to the 'main' carbon line. So for example, pentane, with 5 carbons in a row. Suppose we add 2 methyl to it, one on carbon 2 and one or carbon 3. We'd then have to...

can sm1 tell me why in the michelson morley experiment aeteher is assumed to have a unidorectional constant velocity ?? thankyou so much

Hi everyone! I am new here. I like physics and so I am trying to understand a few things. I think I understood the Newton physics. Now I am reading about relativity. I began wiht special relativity. I just learn the two postulates. I think I can accept them without problems. I also read...

The relation between the angles for which the minima occurs for a Fraunhofer diffraction(parallel rays, large separation between screen and slit) is derived by using the destructive interference criterion. Why isn't there any mention of the criterion for maxima? The results obtained from the...

For small angles theta, the numerical value of sin theta is approximately the same as the numerical value of tan theta.Find the largest angle for which sine and tangent agree to within two significant figures.

is it necessarily true that we have \frac{\partial T}{\partial q}=0?

Hi everyone, I got interested in physics recently and started reading a book called "relativity simply explained " by martin gardener. when i was going through the book i got some doubts in relativity of simultaneity. my problem is described below o>>> ---------------------------<< 0...

I was making a model of a NMOS transistor in Microcap. It was part of an assignment. I was supposed to make graph with changing value of V_{BS}. But after a certain value of V_{BS}, I got negative current. It came to my mind it is not possible. But, I couldn't think of a reason instantly, as to...

in the "derivation" of 'principle of vitual work' Goldstein started with this he wrote the force F acting on each particle as the sum of F_{a} (Force applied) and F_{i}(Constraint force) ok i have some three queries 1)What are constraint forces? 2)Are all internal forces constraint forces 3)He...

While doing experiments on a francis turbine, i noted that the discharge decreases when the load on shaft was increased, =>the speed was decreased. I was(in fact, I am) kind of confused about why it dropped, I did consult some text but didnt get any right reason. I thought that since the blade...

Hi! I need help from someone that knows something about numerical methods in MATLAB. Specifically, fsolve. So, I have an equation L = K(x) - F(x,y). Given the values of L and y, I need to determine the value of x numerically. So, here's what I've done: G(x) = L- K(x) + F(x,y) in the...

If I want to prove that a non specified function f(x) that maps x -->x' is onto could I show that f(x) is one to one and that f(x')^-1 (the inverse function) is also one to one?? Would that be a valid justification to say that thus f(x) must be onto? More specifically I am looking to prove...

For the photoelectric effec to take place for a certain metal, there is a minimum frequency that the incident radiation must have, also called the threshold frequency. Let us call it f_o. The electron is emmitted only when a minimum amount of energy is provided to it so that it can repulse...

I have one doubt about Bhabha scattering which is scattering between one electron and one positron, two oppositely charged particles. Why should they scatter each other away rather than attract and eventually annihilate themselves, giving rise to the pair annihilation process? (This process is...

Hallo friends, I have some Geiger counter for detecting Gamma rays...By this meter one can measure in IPS (Intensity per second) or Siever/hour...Now i need to know What is this new unit IPS...Does anyone heard about it...or does it directly corresponds to the disintegrations per second...

I am just a student of class 11.I got a small doubt ,dont mistake my doubt, i am just a beginner . My doubt is "What is the variation in Ionization enthalpy , electronegativity ,electron gain enthalpy between the isotopes of a element" waiting for my doubt to get cleared .

Doubt on FRAME of REF(Its killing me!Help) Hello Guys I am really fascinated by Theory of Relativity and although its not in my educational syllabus(not a phy scholar) , I really study a lot about it. Now coming to the point , I have a doubt on FoR and it may be basic, so I hope you...

.Please provide me with some help in optics. This doubt is in relation to the use of sign conventions in optics. Whenever we prove anything in optics, say for example, when we prove the mirror formula or the lens formula or the lens-maker's formula, we apply the sign conventions in the...

Keeping the mass constant, if we go on increasing the density of a body its gravity also goes on increasing, like what happens in a black hole,O.K.? But according to the formula F=Gmm/r(square) , only the mass of the 2 bodies is taken into consideration... Suppose 2 spheres are kept at a...

I have a doubt about "doubt" Many non-native English speakers here use the word "doubt" where a native English speaker would use "question" instead. Is this just a random confusion of two words with somewhat similar meanings, or is there some pattern to this? Do these people have a native...

In single slit diffraction, my professor says that only 2 rays get diffracted. Both at the 2 ends of the slit. no other rays are diffracted. Is this true??:confused: What i think is all rays in the slit get diffracted and not only the 2 rays at the 2 ends of the slit.

A thermodynamic/aerodynamic doubt... Hi peeps... Physics forums rock... k now. Before asking my doubt I need to ask small small doubts before the big one... So I guess this question will lead to a hot discussion eventually... Doubt number 1 Is it legal to say that 1 litre of h2o in...

Composite doubt... Composites are so cool and they make me go wild... I have the composite paper only in my 6th semester and I am only in 3rd semester... I was wondering if there are any online calculators to check out the properties of composites. I want to work out with various combinations...

Hi...I am new to this forum. Can somebody clear a fundamental doubt i have?:rolleyes: A wave function has a form found by applying Schrodinger's equation. In steady-state systems, arent the system eigen functions, the wave equation of the system? if so is it the energy eigen function or the...

when we say that in pure rolling the speed of the point of contact is 0 do we really mean it's just absolutely 0 or is it negligible.this may seem strange... but if it's 0 then why does that point ever move.if it ever moves then it's speed is no more 0 ...

folks, in higher secondary books i came across magnet's length that is bar magnet's length is given as " 2l" that is 2 multiplied by l. my question is " why the length is not referred as 'l' the usual way of referring length. please clarify in layman terms. thanks in advance logesh aravindan

A Jet Engine doubt... Hi folks... My aerospace propulsion professor taught me that, in the combustion chamber of a jet engine, during combustion, the pressure instead of increasing, decreases. I have 2 questions. 1) Is it true? 2) If yes, how? How and in what way does temperature, and...

Homework Statement Are H_{2}O and OH_2 same species when used as ligand in complex entity? Can these be used interchangeably? Homework Equations The Attempt at a Solution

http://www.msnbc.msn.com/id/18709539/ The never ending saga...