What is Doubts: Definition and 203 Discussions

Doubt is a mental state in which the mind remains suspended between two or more contradictory propositions, unable to be certain of any of them. Doubt on an emotional level is indecision between belief and disbelief. It may involve uncertainty, distrust or lack of conviction on certain facts, actions, motives, or decisions. Doubt can result in delaying or rejecting relevant action out of concern for mistakes or missed opportunities.

View More On Wikipedia.org
Recent contents Top users
  1. xareu

    Doubts on Ampère's Law and Coaxial Cables

    I have a doubt about Ampère's that keeps me awake at night haha, but I think that for a more knowledgeable person it may seem pretty obvious. I've seen in several books that, in a coaxial cable with equal and opposed currents in the core and shield, the magnetic field outside the outer conductor...
  2. PlasmaHawk

    Doubts regarding Electrical Eng. and Electronics Eng.

    Hello, everybody First some context: I live in Argentina and I'm a few months away from starting my first year of college. In here they make the distinction between Electrical Engineering and Electronics Engineering (and then there's also Informatics Engineering which I think is the equivalent...
  3. M

    Photoelectron to electron hole pair doubts

    Hi, I have a couple of questions on photoelectrons. When a photoelectron of about 3-eV (varies) interacts within 0.2-um depletion region of silicon, what happens? I know, it will generate an electron-hole pair with an efficiency of 1 for 3.6-eV photoelectron. But what happens if the...
  4. B

    Doubts about linear elements of electrical circuits

    First doubt: The impedance Z is defined how Z = R + j X and the reactance X can be wrote how: Source: https://en.wikipedia.org/wiki/Electrical_reactance So, by analogy, the admitance Y is defined how Y = G + j B and the susceptance B can be wrote how what? So: B = \left( \frac{\omega C}{1}...
  5. gracy

    Doubts about Electric field due to an infinitely long wire

    About Electric field due to an infinitely long straight uniformly charged wire my book says the assumption that the wire is infinitely long is very important because without this we can not take vector E to be perpendicular to the curved part of the cylindrical gaussian surface.I think it should...
  6. gracy

    Doubts on properties of electric field lines

    In my book following points have been given 1-due to conservative nature of electric field ,the electrostatic field lines will not form any closed loop.I want to ask how forming a loop makes if non conservative? 2-Field lines have tendency to contract in length (longitudinal contraction )like a...
  7. R

    Doubts on angular momentum [master's degree exam]

    Two hollow spheres, both the mass and radius R M , which are rotating around a center of mass ( CM ) , with an initial period To, are kept distant from each other by an ideal wire with a distance of 8R. At a given instant a motor is driven by wrapping the wire and making the two spheres meet...
  8. R

    Balancing a Redox Equation with Half-Reactions

    It's not clear to me how I can balance the following equation, most of all because of K which I don't know how to deal with: \mathrm{SO_2 + K_2Cr_2O_7 \to Cr_2(SO_4)_3 + SO_3} [this is the text of the exercise] It's acidic solution for sulfuric acid, so the equation can be better written so...
  9. T

    Basic concept doubts in redox reactions

    Homework Statement [C2O4]-2 ------> CO2 Find if the reaction is oxidation or reduction and determine the no. of electrons lost or gained by carbon. Homework EquationsThe Attempt at a Solution I started with finding the oxidation states of both elements. It's 3+ and 2- for carbon and...
  10. Breo

    Have you conquered Peskin's computation challenges?

    Hello everyone,Has anybody already did the computations to reach equations 10.41, 10.44 and 10.45 in Peskin's book? It would be very much appreciated and useful.
  11. Monsterboy

    Doubts about nebulae and star formation

    I read that nebulae are formed by stars exploding and they are also thought to be the birth place of stars. Stars explode when all the hydrogen atoms are fused into heavier elements and they are no longer able to fuse heavier atoms right ? If that's the case then the nebulae should contain...
  12. thegreengineer

    Electric circuits formulas doubts

    Well, recently I have started to deal with electronics and I've seen several new concepts such as ohm's law, parallel and series circuits, what's AC and DC and many other topics. Ok, I have no doubt on what's direct and alternate current or what a series and parallel circuits are; rather than...
  13. A

    IUPAC naming - choosing the main branch doubts

    What are the rules for choosing main branch ? Wikipedia states - "Identification of the parent hydrocarbon chain. This chain must obey the following rules, in order of precedence: 1 It should have the maximum number of substituents of the suffix functional group. By suffix, it is meant that...
  14. B

    Is a Physics PhD For me? last minute doubts

    Hey Everyone, So I was set. I studied and re-took the pgre. I thought long and hard about what I wanted to do in graduate school. I thought about career goals. I talked to professors and graduate students. I even submitted two apps! Two schools that I would be extremely happy to attend...
  15. ubergewehr273

    Length Contraction in Special Relativity

    Could somebody explain the logical reasoning behind lorentz contraction when an object travels faster and faster ?
  16. G

    Engineering Simple Circuit Problem (Clarification of doubts)

    Homework Statement Homework EquationsThe Attempt at a Solution I did a source conversion on the right-most 1A current source to get a voltage source to work with for this question. However, when I tried to work out the solution, my values seem wrong, but I don't understand why, especially...
  17. T

    Various doubts about Black Holes

    Hi there! After giving a thought about this phenomena I came with some doubts and I thought that maybe it was a good idea to put them all together in one thread so I don’t star many discussions simultaneously and also because maybe their answers are related. So here I go: a) As they...
  18. Brunnun

    What are the challenges faced by aspiring theoretical physicists?

    Hello. I'm Bruno, a Brazilian High School graduate that loves high school (and everything I had the capacity to learn) Physics. I plan to pursue a career in Physics, and found some troubles. I did a post on this troubles first (as I didn't read my inbox :P), so if there is anyone out there who...
  19. Brunnun

    Doubts of an aspiring Theoretical Physicist

    I hope I do not extend myself here. I am a Brazilian High School student, graduating this year, that plans to pursue a Physics undergraduate in the United States. Since I started High School I decided on my degree; I love physics and my ultimate dream is to research the depths of the field...
  20. PcumP_Ravenclaw

    Doubts from transposition, fixing and Identity

    Dear All, Please see the attachment for the text i will be referring to. what does "I = τ1 · · · τm, where each τj is a transposition acting on {1, . . . , n}. Clearly, m != 1, thus m ≥ 2. Suppose, for the moment, that τm does not fix n". what does fixing n mean in a...
  21. K

    Elementary doubts i i got confronted with while reading qft

    why should Proca eqn be like ∂γ Fγμ + m2 Aμ = 0 but not ∂γ Fμγ + m2 Aμ = 0 ? another doubt is (λ-1 ω λ)μγ = λ-1 ρμ ωρσ λσγ ? why in λ-1 transformation got upper index in the second place but not in the first place? if someone clear my doubts...I would be thanful... regards.. Kau
  22. D

    Conceptional doubts in making FBDs

    Homework Statement I just have some conceptional doubts and it would really be appreciated if some one would answer! Q1. What is net contact force? Q2. Does it have friction as one of its components? Q3. Is it any way similar to normal force? Homework Equations The Attempt at a...
  23. U

    Doubts regarding gradient operator

    Homework Statement I need some help regarding the gradient operator. I recently came across this statement while reading Griffith's Electrodynamics "The gradient ∇T points in the direction of maximum increase of the function T." Wolfram Alpha also states that "The direction of ∇f is the...
  24. carllacan

    Doubts about the electron magnetic moment.

    Hi. According to this page and other sources I found the z-component of the electronic magnetic moment is greater than the classically calculated value due to relativistic effects. Which makes me wonder: 1) What about the x and y components? I am completely lost as to why only the z axis...
  25. Y

    Some basic conceptual doubts about limits

    (1)If the limit of f(x), as x approaches a point a doesn't exist, and the limit of g(x), as x approaches a point a doesn't exist either, the limit of (f+g)(x) and (fxg)(x), as x approaches a point a can possibly exist? (2)If the limit of f(x) as x approaches a and the limit of (f+g)(x), as x...
  26. S

    Transistor amplification related doubts

    I understand the basic concept. A small change in the base current will lead to large change in the collector current and will lead to amplification. But the question is, the small change in base current is brought by input signal or the biasing? Also the coupling capacitors allow only the ac...
  27. C

    Computer Science theory doubts

    Hi, I would appreciate if someone can check my answers about three questions about computer science and if they are not, what it is missing. Homework Statement 1)Proof that the following languages aren't regular. You can use the pumping lemma and the closing of the class of the regular...
  28. B

    Explanation of the 'chain fountain': some doubts

    Apologies if this has been discussed in other threads already. I did a quick search on 'chain fountain' and got no hits. If you coil a length of chain into a container and let it slip out over the lip under its own weight, it will start to form an arc through the air, without touching the lip...
  29. B

    I love HEP Theory, but doubts about future.

    Hello! This is my first time starting my own thread and I have spent a lot of time reading other threads and posts about Physics grad admission. My post is not really about "WILL I GET ACCEPTED?" per say, but I just need a place to write about how I feel and for some reason I feel like doing it...
  30. B

    Solved: EES Homework Questions for Thermodynamics Exam

    Homework Statement Hello! I'm studying for a Thermodynamics exam and I need to solve these problems in EES (Engineering Equation Solver). Below the questions, there's my resolution. Can someone confirm if they are right? 1) The vapor quality of water, using u=2000 kJ/kg and s=6 kJ/kg×K...
  31. ShreyasR

    Some basic doubts regarding transistors characteristics

    1) While plotting input characteristics of a transistor, we choose to keep output voltage constant and plot the variation of input voltage and current. Why do we choose to keep output voltage constant and not current? 2) While plotting output characteristics of a transistor, we choose to keep...
  32. K

    Reactions at beam ends when varying load position - clearing doubts

    Homework Statement Well actually we were doing a beam experiment in class. It consisted of varying the position of a load and measuring the reactions to eventually analyse the relationship between the distance of load from 1 support with the 2 reactions. The reactions were provided by two...
  33. S

    Managing doubts in an semi automated learning system

    in a classroom teacher are asked doubts on the topic taught by students . they are critical in helping their understanding of concept. what can be the extra information that may be useful for the teacher that can be asked along with the doubts in an doubts query form?
  34. N

    Programs Doubts about a master degree after Computer Engineering

    Hi everyone, this year i'll get my Bachelor Degree in Computer Engineering, i have some doubts about the master course to get; actually my university offers these courses in accordance with my Bachelor Degree: (i'll write only those who catched my interest) - Computer Engineering ...
  35. FOIWATER

    Is Gauss' Law Applicable for Non-Uniform Charge Densities?

    I actually have solved the problem and received the answers that the book provided. However I am second guessing what I did, This is the problem: let rho v be 10/r^2 mC/m^3 between 1<r<4 let rho v be zero elsewhere a)find the net flux crossing the surface at r=2 m, r= 6m b)determine...
  36. J

    Doubts on the boundary conditions of PDE

    Hi all, Say I am solving a PDE as \frac{\partial y^2}{\partial^2 x}+\frac{\partial y}{\partial x}=f, with the boundary condition y(\pm L)=A. I can understand for the second order differential term, there two boundary conditions are well suited. But what about the first order differential term...
  37. M

    Momentum: History & Newton's 2nd Law

    A body with mass 'm' moves with velocity 'v' possesses momentum and the magnitude of momentum of the particle is given by product of its mass and its velocity Who came up with this idea? On what observation leads to think him like this? I know that Newton's 2nd law states that force is nothing...
  38. M

    Velocity in Classical Mechanics by Douglas Gregory

    i am using textbook in classical mechanics by douglas gregory. It is known that rate of change of displacement with time is velocity , but it is given that the velocity at any instant is the equal to the product of speed and its unit tangent vector at that instant in vector form i.e, V=vT (this...
  39. T

    Doubts on 2D and 3D Ising Model

    Considering d=2 or d=3, the Ising model exhibits a second order phase transition at the critical temperature T_c, where the system goes from an ordered phase (spins preferably aligned in a certain direction) to a disordered one. This is reflected by the behaviour of the susceptibility, similar...
  40. DanielSauza

    Engineering Mech Engineering Doubts - Get Advice Here!

    Hello, I've been studying mech engineering for the past 2 years but over the past month I've been reading about other people's ME program and I'm not sure if mine is good enough. Would anyone be kind enough to tell me what subjects you took or are taught commonly during ME? Also, sorry for...
  41. C

    Help With Circular Motion Doubts

    Hello! I have a few doubts in circular motion and I'd really appreciate your help :) 1) There is a statement in my book ( I have attached images - the first one) according to which the only horizontal force towards the center on the vehicle is friction. I know that some centripetal force is...
  42. W

    General Doubts on Ehresmann Connections

    Hope someone can help me clarify a couple of issues about Ehresmann connections and vertical spaces. My main issue is how to define the tangent space at a point in a _general_ fiber F in a fiber bundle (and not just when F is either a vector or a manifold If I understood correctly)...
  43. P

    What are Some Unresolved Questions in Electrostatics?

    I have a few questions pertaining to some concepts in electrostatics, I'd be grateful if someone would help me out. 1) When we place a positive point charge inside a hollow conducting sphere, at its center, field lines emerge uniformly from the sphere. Okay, easy enough. Now, if we place the...
  44. N

    Is Stokes' Theorem Intuitively Satisfying and Accurate?

    Stokes' Theorem says the curve integral of any surface S simply equals the counter-clockwise circulation around its boundary-curve C.How can this be right? Let's say you have a hemisphere surface S with centre in origo, and its shadow on the xy plane. Both surfaces will have C as their boundary...
  45. ShreyasR

    Doubts about basics of superconductivity.

    I am just introduced to basics of superconductivity in Engineering Physics. My lecturer asked a question: Is the resistance of a superconductor zero or close to zero? And my answer was close to zero. I have read that the resistance of a superconductor is exactly zero, but then when I put some...
  46. ash64449

    Doubts in general theory of relativity

    according to equvalence principle,acceleration can be equvalent to rest in which gravitational field exists. Earth revolves around the sun as sun produces curvature in space-time. What kind of acceleration is the curvature of space-time produced by sun equavalent too?
  47. ash64449

    Doubts in special theory of relativity

    Hello friends, From special theory of relativity,it is understood that if two events are simultaneous to a stationary reference frame,it is not simultaneous to a reference frame that is moving uniformly in straight direction. Is opposite possible? That is are two events are simultaneous to a...
  48. I

    Doubts about potential energy, bonding and chemical reactions

    Hello everybody, First, sorry for the bad english, it is not my language. I have a few theoretical problems and I would be very thankful if you helped me. 1º: I see the graphic about covalent bonds and potential energy a lot of times and they always say that potential energy...
  49. P

    Doubts on Rotation: Seeking Physical Understanding

    I have some doubts on topics related to rotation, so I thought I'd make a single thread rather than multiple ones. 1. Why are the Coriolis and Centrifugal forces "fictitious"? I think I might be getting confused by the terminology, but do they represent physical forces? My lecture notes say...
  50. iVenky

    Doubts in Epitaph of Stevinus .

    Doubts in "Epitaph of Stevinus". I have attached the link for the image- http://1.bp.blogspot.com/_YthztMsYjr4/TMB3Wmis2fI/AAAAAAAABR4/xBmLusI58AU/s400/epitaphofstevinus.png I can understand that the weight of the body should be proportional to the length of the line. What I can't...
Back
Top