What is Doubt: Definition and 591 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.

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  1. P

    Engineering RLC Circuit (lab session doubt)

    Homework Statement I have to answer a few questions about a lab session I did (university) and I'm really stuck with this one. The objective of the lab session was to find the self inductance (L) of a solenoid. In order to do that, I had a function generator exciting a solenoid with a high...
  2. F

    Doubt about abelian conjugacy class

    Homework Statement I'm kinda lost in the concept of conjugate elements in group theory. It says that a element "h conjugate by g" is: g-1×h×g = hg Then it says that if the group is abelian h = hg Homework Equations Abelian group: a*b = b*a The Attempt at a Solution I don't get why the fact...
  3. thegreengineer

    What does 0 V exactly mean in an electric circuit mean?

    I'm a mechatronics engineering student, and I know that electronics is a requirement in most engineering programs. I'm been dealing with electronics recently and I've been studying electric circuits. I've been noticing that in some of them instead of being closed (in diagrams) they are like...
  4. A

    A doubt on the meaning of the bra ket product

    Hello everyone, I have thi doubt: If I have a state, say psi1, associated with the energy eigenvalue E1, the integral over a certain region gives me the probability of finding the particle in that region with the specified energy E1. Now if I put an operator between the states I obtain its mean...
  5. L

    Transistor as an amplifier (doubt)

    The npn transistor is said to function as an amplifier only in its active state (emitter base is forward biased and collector base is reverse biased). It is considered that majority of the electrons reaching the base layer is dragged into the collector layer. So the emitter current (ec) is...
  6. P

    Doubt about a answer on a test

    Hello everyone, A few weeks ago I got a test about physics. One of the questions on the test was about a satelite that would go to an other planet, it was doing system tests in orbit, we had to tell if the satelite had weight. I understand it doesn't, because it is falling and so doesn't apply...
  7. lawofnature

    Can someone explain this thermodynamics related doubt i have?

    Assume a piston cylinder arrangement. External pressure always equals internal pressure ( reversible conditions ). Now consider these two scenarios: Scenario one: q heat is suddenly added to the arrangement causing a temperature rise and consequently pressure rise, but the volume is yet...
  8. P

    Acceleration in circular motion -- conceptual doubt

    Homework Statement Purely a conceptual/ terminology question, a simple yes or no will suffice :) In circular motion, will a point on its circumference will have a LINEAR acceleration which can be broken into two components- the RADIAL component which is v2/r and the TANGENTIAL component which...
  9. F

    Why do we take component of v1 along the string in Newton's laws homework?

    Homework Statement Homework Equations None... Newton's laws The Attempt at a Solution Not the attempt, the entire solution is: String length is constant...hence if on the right side of the pulley, the string goes up by x distance then on the right side also the string goes down by x...
  10. thegreengineer

    Basic Electronics: Transistor confusion

    So, recently I started learning about electronic components and then I started learning about semiconductors. The one which I've been having some real trouble to understand its function is the transistor. So I bought an electronics textbook called El ABC de La Electrónica (The ABC of Electronics...
  11. AdityaDev

    How is the Electron Configuration of Central Atoms in Complex Salts Determined?

    I am confused with the electron configuration of central atoms in complex salts eg. ##[Fe(CN)_6]^{2-}## configuration just Fe atom is Now the complex is low spin so the configuration becomes, Now we have 6CN. where will they donate their electrons? Will the donate electrons in the remaining...
  12. basheer uddin

    A doubt in angular momentum problem

    Homework Statement if a disk is rotating on another stationary disk and someone standing on the stationary disk stops it what will the final angular velocity of both the disks be? the catch is that both the disks are not co axial. assume ω angular velocity, M mass of big disk.m mass of small...
  13. AdityaDev

    Optics Homework: Converging Lens and Varying Refractive Index

    Homework Statement A rectangular slab of length l=20cm and thickness d=4cm is placed in left of a converging lens of focal length f=20cm. A screen is placed in the focal plane plane of lens (right side of lens).Refractive index of the material of slab increases linearly from u0 at the bottom by...
  14. AdityaDev

    Modified plano-convex lens doubt

    I was thinking about the situation given my text about a plano convex lens which was produced with a manufacturing defect. It's plane surface is tilted outwards by a small angle 'z'. In the text its written that when a parallel light beam enters the lens parallel to x-axis , it will still be...
  15. PcumP_Ravenclaw

    Doubt about condition solutions of complex line equation

    Dear All, Please help me clear some doubts about Theorem 3.3.1 in the 1st attachment. The condition ## |a| = |b| ## has only 8 cases right? ## { x+iy. x - iy, -x + iy, -x - iy, y + ix, y - ix, -y + ix, -y - ix } ## so for the condition ## |a| = |b| ## and ## b \bar c = \bar a c...
  16. AdityaDev

    Understanding Buoyant Force: Exploring FBD and Equations in Accelerating Vessels

    If I have an object of mass m tied to the lower surface of a vessel having a liquid and the vessel accelerates upwards... From FBD of object, Buoyant force acts upwards, mg down, pseudo force downwards (frame of reference is vessel) T down. Here's the doubt. Why is F(buoyant force) = Vp(g+a)...
  17. AdityaDev

    Understanding Surface Tension and the Role of Force in U-Shape Wire Frames

    If I have a U-shape wire frame and it contains a straight sliding wire and I dip this in soap, a film forms between the sliding wire and the boundary of U shape frame. Why is the force due to surface tension F = 2Tl where l is length of sliding wire? They say there are 2 layers in contact...
  18. J

    A small doubt about electric flux

    Hey there... As far as I know, electric flux is a scalar quantity which means that negative values are smaller than zero. This concept really confuses me since most of the exercises I dealt with suggest that negative flux somehow is larger than zero flux Example 1 the uniform field is directed...
  19. ubergewehr273

    Time Dilation: Doubts & Questions Answered

    Why must time slow down when a body moves with respect to a reference frame at rest ? Why should its mass and length increase and decrease respectively when a body travels faster and faster ?
  20. ubergewehr273

    Is Fire or Electricity Considered a State of Matter?

    Is there any state of matter for fire or electricity ? If yes, then what is the state of matter ?
  21. N

    Doubt with Newton's 3rd law

    I understand that if for an instance one object pushes another with a determinate force, the other object acelerates with that force, and the pushing object acelerates in oposite direction with the oposite force as well. However if I punch a piece of paper I don't feel the same oposite force...
  22. F

    Quantum Energy Doubt: Solving a Particle Problem

    Homework Statement Hi, I have a problem related to some quantum concepts. One teacher of mine has tasked me with solving the next problem: Given a particle on its fundamental state in a potential pit of width a, V=0 between 0 and a and infinite at the rest of the space. Suddenly, the width...
  23. AdityaDev

    Doubt in parallel plate capacitor

    I was going through the capacitor lesson in my textbook. In it its written "...both positive and negative plates will produce electric field in the same direction, hence the electric field adds up...outside the plates, electric field is zero since the field due to negative and positive charges...
  24. Breo

    Doubt: Why Quadratic in Matrix but Power 4 in Einstein-Rosen Metric?

    I have a doubt since I see the next equation and the corresponding matrix: $$ ds^2 = \Bigg( \frac{1-\frac{r_s}{4\rho}}{1+\frac{r_s}{4\rho}}\Bigg)^2 dt^2 - \Big(1+\frac{r_s}{4\rho}\Big)^4 (d\rho^2 + p^2 d\Omega_2^2) $$$$ g_{\mu\nu} = \left( \begin{array}{ccc} \Bigg(...
  25. U

    Understanding the Conversion Formula for Venturimeter Readings

    Hi all I was trying to solve some numerical problems on venturimeter. I got stuck due to a formula, that I was not able to make sense of. It is a conversion of reading of differential manometer in mercury to corresponding reading in water. I've attached the question, please help me understand it.
  26. PcumP_Ravenclaw

    Doubt about rotation isometry on the complex plane

    Dear All, In the 2nd paragraph of the attachment can you please explain to me why we are trying to make ## r(z) = z ## and what does "As r is not the identity..." mean?? and how did the line ## L = 0.5*b + ρe^{θ/2} ## come about? Danke...
  27. Prashasti

    Understanding the Role of Convex Lenses in Fraunhofer Diffraction

    Homework Statement A monochromatic source of light 'S' is placed at the principal focus of a convex lens 'L1'. A parallel beam of light or a plane wave front is incident on the narrow slit represented by AB (its width - 'a') Homework Equations So, what my teacher did was, She showed...
  28. PcumP_Ravenclaw

    Doubt about the solutions of the equation aZ + bz + c = 0

    Dear all, can you please help me show why the 2nd scenario below has no solution... Theorem 3.3.1 Suppose that a and b are not both zero. Then the equation ## aZ + b\bar Z + c = 0 ## has a, b and c are complex numbers. Z is the unknown complex number. (1) a unique solution if and only if ##...
  29. S

    Doubt about Frame Dragging and planetary revolution

    Our sun rotates in counter clockwise direction and hence frame dragging will be also in that direction. Suppose if we put a satellite in sun's orbit (almost circular) to revolve in opposite direction to the sun's spin, what would happen to the orbit of the satellite? Would it fall into the sun?
  30. V

    Conceptual doubt in a rotating ring

    Homework Statement A metal ring of mass m and radius R is placed on a smooth horizontal table and is set rotating about its own axis with a constant angular speed ω. What is the tension in the ring ?Homework EquationsThe Attempt at a Solution Consider a small element ds=rdθ .Tension T acts at...
  31. F

    Electrodynamics, multipolar development doubt

    Homework Statement In the XY plane there are two point charges +q at (0, -b, 0) and –q at (0, b, 0) and a ring of radius a centred in the centre of the plane: Find the electric field in all points of the z axis and study the field’s dominant behaviour at distances z >>a,b. Find the electric...
  32. P

    Convergence Doubt: Is Most Repeated Value the Answer?

    Hello people, In case if I am typing the question in the wrong forum please redirect me. OK, here it goes... I have this stupid question: Suppose we have a sequence 1, 1, 1, 1, 1, 1... It converges to '1'. Consider 1, 0, 1, 0, 1, 0... it diverges right? What about a sequence 1, 1, 0, 1, 1...
  33. J

    Piezoelectric coupled governing equations doubt

    Hi , can anybody make me sense of these equation on which i am striking my head for last 2 months. I am trying to understand piezoelectric effect. And in process of which i came to see so called strain based form of equations related to direct(Equation no.2) and reverse(Equation no. 1)...
  34. F

    Electric Field in Conductor w/ Infinite Length & Density ƍ

    Hello, I have a doubtaboutthe use of Gauss theorem in the presence of a coductor. If I have a infinite cylindric long shell with a charge density ƍ of radius b and inside of it a cylindrical conductor of radius a, also of infinite lenght, what will be the electric field in a point located...
  35. D

    Solving Doubts When Showing Simple Properties of Norms

    Sorry, I wasn't sure of the best way to phrase this. This is a common problem I keep having. Here's the definition of a norm: Let E be a vector space V defined over a field F. A norm on V is a function p: V \rightarrow \mathbb{R} such that: \forall a \in F and \forall u,b \in V: (i) p(av)...
  36. L

    Possible webpage title: Can Two Universes Be Exactly the Same in MWI?

    Hi to all. :) First of all I'm not cleary a physician, not even an amateur, only a writer and i hope that a so low level of knowledge don't offend anyone ^^' (my bad level and my broken english :look: ) So: I have a question about the MWI. According with the most serious interpretation: we...
  37. M

    Having a doubt in breaker and cable selection

    hello i have got a 150A breakerMCCB and the cable connected is 95sqmm and load current is 135A is this correct or any changes is to be made? what will happen if the supply is given from 420v 3phase system
  38. V

    Doubt in Gravitation: Understanding the Orbital Motion of Two Stars

    Homework Statement Suppose two stars are orbiting each other in circular orbits with angular speed ##\omega## .M1 is at distance r1 from CM wheras M2 is at distance r2 such that r1+r2=d where d is the distance between them . Now i have a little doubt whether the stars are orbiting around...
  39. basheer uddin

    A small doubt in a limit problem

    Homework Statement find limit ##\lim _{ x\rightarrow \infty }{ \frac { { 10 }^{ x } }{ x! } } ## Homework Equations l'hopitals rule The Attempt at a Solution on substitution we get ##\frac { \infty }{ \infty } ## on using l'hopitals rule,what is the result of differentiation of x!? or...
  40. M

    Why is the range of ø in spherical coordinates limited to 0 to π?

    Homework Statement In spherical coordinates (ρ,θ,ø); I understood the ranges of ρ, and θ. But ø, still eludes my understanding. Why is ø only from 0 to π, why not 0 to 2π??
  41. U

    Doubt regarding Taylor's theorem

    Homework Statement In Taylor's series, the Lagrange form of remainder is given by R_n = \dfrac{f^{n+1}(t)(x-a)^{n+1}}{(n+1)!} \\ t \in [a,x] whereas my book states that it is given by \dfrac{h^n}{n!} f^n (a+ \theta h) \\ \theta(0,1) I don't see how these two are interrelated. Can...
  42. jmex

    Lever Rule: Determining Amount of Liquid & Solid

    Hello, From the figure how is it possible to say that this line shows amount of liquid while other is amount of solid. In the figure they showed MP is amount of liquid while OM is amount of solid. How?
  43. Uday

    A Doubt Regarding Quantization of charge ,its relevance in integration

    a) We know that the smallest charge that can exist is 'e' . But in several instances (such as calculating potential energy of sphere of charge ) we consider 'dq' and then integrate it . How can we justify this ? b) We know that 1/2 or 1/3 of e (charge of electron) doesn't exist . But...
  44. Hardik Batra

    Electric potential energy definition doubt?

    Electric potential energy of a charge q at a point in an electric field due to any charge configuration as the work done by the external force in bringing the charge q from infinity to that point without any acceleration.. In this definition, why charge is moved without any acceleration?
  45. T

    Simple doubt in superposition of waves

    Homework Statement While analyzing superposition of waves from two coherent sources ,the displacement from the two sources are written as y1=A1cos(kx-ωt) and y2=A2cos(kx-ωt+∅) .The resultant displacement at any point is given by y=y1+y2 . I am having doubt that why does argument of sine in...
  46. F

    Engineering Doubt about BCD Sum circuit using full adders

    Homework Statement I understand this BCD sum circuit. The only thing that I'm not understanding is why last full adder carry out also triggers an 6-sum in the other part of the circuit. I mean, if the nibble is not an valid BCD number, we sum six to the number. Not valid BCD numbers are...
  47. K

    Doubt in a scene from the movie Gravity

    Doubt in a scene from the movie "Gravity" In the movie gravity, there is a scene where Dr. Ryan Stone (Sandra Bullock) detaches herself from the broken but moving arm of space shuttle (till 0:45 in the following link): https://www.youtube.com/watch?v= As soon as she does, she spins so...
  48. T

    Conceptual doubt - Rotating nonconducting ring

    Homework Statement Consider a non conducting ring of radius r and mass m which has a total charge q distributed uniformly on it.The ring is rotated about its axis with an angular speed ω. a)Find the equivalent electric current in the circuit. b)Find the magnetic moment μ of the ring...
  49. S

    What do the integration limits 5- and 10+ mean in Signals and Systems?

    I saw in a question related to Signals and systems that the limits were taken from 5- to 10+ where the signs were in the feet of the numbers..lol..i don't know what you call that. What does this mean?
  50. E

    Doubt in equilibrium of rigid body

    Hello there! I am currently studying the equilibrium of rigid body and encountering a doubt. Now, in their explanation of reaction forces by a roller or a rocker or a smooth surface, they generalize it as in the preceding examples prevent the translation of a beam for example in ONE direction...
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