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  1. Zahid Iftikhar

    Time of Impact of Gas Molecules on the Inner Wall of a Pressure Vessel

    In derivation of relation for pressure of Gas ,(see pic below) the time for rate of change of momentum of molecules should be the time for which the wall of the vessel and the molecules kept interacting with each other, not the time between successive collisions. As circumscribed below, my...
  2. Zahid Iftikhar

    I Stability of Nuclei

    Hi I need help from PF scholars to figure out one difficulty in understanding stability of nucleus. Nuclei remain unaffected during chemical reactions taking place even at very high temperatures and pressures. But their binding energy figures are not that high. Such chemical reactions have heat...
  3. Zahid Iftikhar

    Voltage across R, L and C vs AC Voltage source in RLC Series Circuit

    One property of series resonance circuit is that at resonance, the voltage across circuit elements R,L and C may be larger than the source voltage. I can relate it to vector analogy where component vectors may have larger values than the resultant and the phenomenon is counter-intuitive. This...
  4. Zahid Iftikhar

    Why does a capacitor charge to 63% of the applied voltage?

    Statement of problem is given in the summary. Mathematics proves time constant is calculated from the equation V= V0 exp t/RC I want to know if there is any physical explanation of this effect. Please guide me on this. Regards
  5. Zahid Iftikhar

    Electric Field of a moving charge

    When a charge is at rest, it has an electric field only. When the charge starts moving , it is said to have accompanied a magnetic field. My question relates to its electric field while in motion. Does it still exist or not? I know in electron guns electrons are deflected while passing thru the...
  6. Zahid Iftikhar

    Charge on plates in Millikan's Experiment

    When a capacitor is connected to a battery, it gets charged according to the voltage of the battery. If battery is disconnected, the charge stays on the capacitor. In Millikan's experiment used to find charge on an electron, when two plates are connected to a voltage source, they acquire...
  7. Zahid Iftikhar

    B Why do metastable states in atoms exist?

    Hi My question relates to existence of metastable states in atoms which help out laser production. Is there any physical reason why some orbits allow electrons to stay for comparatively longer time 10-3 s than others which allow only 10-8s? Is this stay time same for all materials? Please guide.
  8. Zahid Iftikhar

    I Quantities unchanged in Two Inertial frames

    My question is about some physical quantities which two observers in two respective inertial frames will find the same. I wonder are there any such quantities? Some books say force, speed of light etc are constants for both the observers. Please guide me on this. Regards.
  9. Zahid Iftikhar

    I Hysteresis curve behavior

    Please help in the explanation of BH curve (See attached file). At the starting point, more current is required to bring the material to its magnetic saturation point( in fig form origin to pt.a shown by purple line ) as compared to when the material is fully demagnetized and then brought to...
  10. Zahid Iftikhar

    Temp and Pressure measure of KE(average)

    Hi My question is related to interpretation of temperature and pressure in gases on the basis of kinetic molecular theory. According to it, both temperature and pressure are proportional to average translational kinetic energy of the gas molecules. Now in a situation where an ideal gas in...
  11. Zahid Iftikhar

    I Ejection of Only one electron by a Photon in the Photoelectric effect

    Hi I am surprised to know why only one photon in photoelectric effect ejects one electron only. What if a high energy photon (not necessarily x-ray or gamma ray, which may cause Compton effect or pair production)hits the metal, say it has energy double or triple of that of the work function? Why...
  12. Zahid Iftikhar

    Magnetic Field of an AC generator

    Hi Please help me in understanding the kind the magnetic field used in an AC generator. Most of the figures (one shown in attached file) are shown with concave poles. Hence the field has to be radial. In such a field the angle between plane of coil and the magnetic field remains zero all the...
  13. Zahid Iftikhar

    Adjustment of Significant Figures

    Homework Statement The diameter and length of solid cylinder measured with a vernier calipers of least count 0.01 cm are 1.22 cm and 5.35 cm respectively. Calculate the volume of the cylinder and the uncertainty involved within it. Homework Equations V= 1/4 πd2 l The Attempt at a Solution...
  14. Zahid Iftikhar

    Bernoulli Equation and gauge pressure

    Homework Statement What gauge pressure is required in the city mains for a stream from a fire hose connected to the city mains to reach a vertical building of height 15m? Homework Equations Bernoulli Equation The Attempt at a Solution I have tried this sum. My confusion is regarding choice of...
  15. Zahid Iftikhar

    I Helium Neon Laser

    I need help to understand the energy transfer mechanism in Helium Neon Gas laser. When helium atom is excited and staying in its metastable state, it is said to have collision with neon atom and thus transfers its 20.61eV energy plus some of its kinetic energy 0.05eV to enable neon atom to reach...
  16. Zahid Iftikhar

    Collimation of an Electron Beam by the Anode of a CRT

    Please help me in understanding the function of anode. As in image attached you see, once the electron beam is emitted from cathode and filtered by grid, it enters into the one or series of anodes. As anode is positively charged, so, to my understanding it has no electric field inside its hollow...
  17. Zahid Iftikhar

    I Comparison of movement of Disc and Hoop

    A disc and a hoop (ring) both of same mass and radius roll down an inclined plane of height "h". It is well known the disc has great velocity than that of the hoop at the bottom. I am fixed in the situation after they start rolling horizontally. Which will go farther? If the surface is...
  18. Zahid Iftikhar

    Electric Potential midway between a pair of equal opposite charges

    Hi I need help to understand how electric potential could be zero at the center of two equal but opposite charges. It seems, there is a no field free region anywhere inside the space between the charges. If I move a test charge from negative to positive charge or otherwise, there seems to be no...
  19. Zahid Iftikhar

    Uniform Field due to an Infinite Sheet of Charge

    Hi I have read one excellent explanation on the question I am posting again, at another thread on PF, because I am not able to completely understand the concept. Please spare some more time. I need help to understand how an electric field due to an infinite sheet of charge can be uniform where...
  20. Zahid Iftikhar

    Problem related to the Bernoulli Equation

    Homework Statement What gauge pressure is requried for water in a water supply line to reach a vertical height of 15m? Homework Equations Bernoulli Equation The Attempt at a Solution I have tried this numerical by taking velocity at ground level to be equal to velocity at top i.e. 15m height...
  21. Zahid Iftikhar

    How to solve using Bernoulli equation

    Homework Statement What gauge pressure is required by city mains for a stream from a fire hose connected to the mains to reach a vertical height of 15m? Homework Equations Bernoulli Equation: The Attempt at a Solution
  22. Zahid Iftikhar

    Bernoulli Equation and Leakage in a Pipe

    Hi boneh3ad Your discussion on Bernoulli Equation was very impressive and helped me a lot to understand this rather complicated equation. I have a question which puzzles me a lot when I want to solve it using Bernoulli equation. Here is the statement. " If there is some fluid flowing thru a...
  23. Zahid Iftikhar

    Why is EMF generated by changing magnetic flux? please help

    I am fixed to find out the reason what makes the charges get separated in conductor causing an emf leading to induced current. A very good reason exists for motional emf. It can be explained with the help of F=qvBsinΘ.
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