Recent content by Steve4Physics

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    Shape of equipotential surface in 3d

    Yes. That’s right. On a (2D) drawing for a charged sphere, we would show equipotential lines which would be circles. In real (3D) life, we actually have spherical equipotential surfaces, (because we have spherical symmetry). On a (2D) drawing for a charged infinite cylinder, we would show...
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    Shape of equipotential surface in 3d

    Try a couple of easier questions first: 1) What shape are the equipotential surfaces around a uniformly charged sphere? 2) What shape are the equipotential surfaces around a single uniformly charged infinite cylinder?
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    Shape of equipotential surface in 3d

    Hi @Lochikilebor. Welcome to Physics Forums. The way it works here is that we help/direct/advise you so that you can work out the answer for yourself. (Take a look at some of the other threads.) We don't do the problem for you! Read the forum rules here...
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    A problem in this photoelectric effect experiment

    Yes. The other typo's I can spot are also important: ________________________ "The switch is in position while radiation with wavelength 140 nm is incident ..." should be "The switch is in position b while radiation with wavelength 140 nm is incident ..." ________________________ "(f) The...
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    A problem in this photoelectric effect experiment

    Because 334 Ω is the last value given for R (in part (b)) and the question tells you when R is changed. And, as far as I can see, you need the value of R to answer question-parts (d) and (e). Any comments on what I said in Post #2 by the way?
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    Problem in understanding angular momentum of a rigid body

    I'm not clear about this myself, so won't attempt a direct answer. But maybe this will help. Let me quote from this link: https://galileoandeinstein.phys.virginia.edu/7010/CM_27_Eulers_Equations.html “..but we’re looking at the changing angular momentum, why isn’t the angular momentum just...
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    A problem in this photoelectric effect experiment

    But to actually answer your question... I is the current through the variable resistor (presumably still set at 334 Ω). What is the current through the battery in terms of I and i? What is the current through the fixed resistor in terms of I an i? Then consider the loop containing only the...
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    A problem in this photoelectric effect experiment

    Hi. Welcome to PF! A few comments... But the value of 'position' is missing! Presumably position b? But your anwer to part (a) says the photocurrent is zero - which conflicts with the information in the question. You give the equation "e|V_AB|=hυ-φ". I would use ##V_S## (stopping potential)...
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    Flux linking (and de-linking?)

    You gave the question immediately followed by what appears to be your answer. So I assumed that it was your answer! What was the purpose of what you wrote, if it was not an attempt at an answer? You then gave the mark scheme followed by a question about the mark scheme. Coils A and B share the...
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    Flux linking (and de-linking?)

    The mark scheme is simply stating that the flux (created by the current in coil A) is linked to coil B. This is always true - whether the flux is constant, increasing or decreasing. By the way, you haven't really answered the question. 1) You haven't explained (in terms of magnetic flux) the...
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    UK School Physics Exam from 1967

    For anyone interested in ‘what it used to be like’… Sifting through some old paperwork, I found one of my 1967 A-level physics exam’ papers. For those unfamiliar with UK ‘A-levels’ in 1967, they were national examinations generally taken in school at about age 18. Students typically studied 3...
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    Absolute motion analysis of pulley-spring system

    Nice idea to show what's going on! In the above attachment it might avoid possible confusion if: - the centre of the left lever is shown moving a distance d (unmarked at present); - the right end of the left lever is shown moving a distance 2d (marked as 'd' at present).
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    Absolute motion analysis of pulley-spring system

    I think the problem is that you are working out ##s_B##, which is the position of pulley B. But that’s not what you need to work out! Try this... Each pulley has it’s own rope, one end of the rope is fixed to the ceiling, the other end is 'moveable'. We need to consider the movement of: -...
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    Absolute motion analysis of pulley-spring system

    Correct. But you are not being asked how far the right pulley moves. Say the rope is attached to the spring at point Q (end of rope). The spring is stretched by an amount equal to the distance moved by Q. You need to find how far Q moves. This is not the same as the distance moved by the...
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    Absolute motion analysis of pulley-spring system

    Hi. Consider the left-pulley and the rope around it. One end of this rope is fixed to the ceiling and the other end is attached to the (centre of the) right-pulley at point P. Q1. If the left-pulley moves down a distance x, how far does P move? Q2. You now know how far the right-pulley moves...
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