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  1. K

    Longitudinal vibrations in solid metal rods

    Hi Rajini, Thanks for the reply. But i guess it still doesnt address the question why the presence of the holding fingers force that location to become a node. Any other responses from the experienced forummers please? Thanks!
  2. K

    Longitudinal vibrations in solid metal rods

    Hi people, I have a question which i hope you helpful guys/gals can help to shed light on. We all know when we strike one end of a solid metal rod with a hammer sideways (i.e. from left to right), longitudinal vibrations will be set up across the length of the rod. Textbooks and websites...
  3. K

    Standing waves in a metal rod

    Hello friends, I have done some research on the Internet about producing standing waves in a metal rod, and how the various harmonics frequencies are being derived. I have two questions that i wish to discuss here: 1. Is the pattern of standing waves and method of formula derivation the...
  4. K

    Some confusion between radiation and conduction

    Hi Magpes, Thanks for the reply. I can understand why you said radiation through metals is negligible, as there are many mobile electroons which will make conduction the predominant process. But i cant fully understand why radiation through air is negligible if the temp is less than...
  5. K

    Some confusion between radiation and conduction

    "I pour hot water into a metal container. The inside surface of the container gets hot." It is quite clear the inside surface gets hot due to conduction (criteria of process is satisfied). What i am not so sure about is whether radiation is involved. Theory and some gut instinct tells me...
  6. K

    Greenhouse effect (reflection vs transmission)

    Thanks a lot for the replies! :!!)
  7. K

    Greenhouse effect (reflection vs transmission)

    Hi, In the study of the greenhouse effect, I know for a fact that short wavelength radiation pass through a glass container and heat up its contents. When its contents get hot, they will re-emit longer wavelength (and hence lower energies) radiation, which will then be unable to pass through...
  8. K

    Questions on Heat (tricky)

    1. Homework Statement Jack took two glass bottles containing water at 20 degC and wrapped them separately in washcloths. One of the washcloths was wet and the other was dry. Twenty minutes later, she measured the water temperature in each bottle. The water in the bottle with the wet washcloth...
  9. K

    Comment: When a metal is heated, there is current (ie flow of e) flowing too

    Comment: "When a metal is heated, there is current (ie flow of e) flowing too" "We all know that metals are good conductors of heat. When one end of the metal is heated, the electrons will rapidly transfer the energy to the other end. This energy transfer often involves the flow of electrons...
  10. K

    From Celsius to Kelvin - why +273?

    Hi, I am puzzled by the use of the number 273 when converting from Celsius to Kelvin and vice versa. I know that Celsius scale is based on ice point and steam point, whereas Kelvin scale is based on triple point of water, which is very very close to ice point. I am a teacher and i was...
  11. K

    Difference between plano-convex and biconvex lens

    Thanks a lot to all those who have applied. This forum is a great resource haven. So to conclude, a better way to have a better telescope will be to have the 2 plane surfaces facing each other. The curved surfaces will then face the light source and the observer's eye respectively. Is this...
  12. K

    Difference between plano-convex and biconvex lens

    Hi all, I am implementing a lab activity for a 2 lens set-up that will serve as a simple telescope. In the teacher's manual, it lists down 2 plano-convex lenses, with the 2 curved surfaces facing each other. The plane faces will respectively face the light source and the observer's eye...
  13. K

    Absolute voltage values at battery terminals

    Thank you both for the wonderful and insightful replies.
  14. K

    Absolute voltage values at battery terminals

    Hi all, Lets say i have a battery with a rated voltage of 3V. This means that there is a potential difference of 3 V across the +ve and -ve ends of the battery. This can mean 3V/0V, 5V/2V, 6V/3V and the list of possible combinations goes on. My question: Is there any way of knowing the...
  15. K

    Lighting up a fluorescent lamp with a Van De Graaf generator

    Hi all, Let's say i have the following: I approach a charged-up VDG holding a fluorescent lamp. The end nearest the VDG is labelled A and the end furthest away from the VDG is labelled B. My hand is holding the lamp in the middle, i.e between ends A and B. The region inside the lamp...
  16. K

    What happens to the current when lightning strikes a swimming pool?

    Thanks Delphi 51! Physics forums beat any textbook hands down.
  17. K

    What happens to the current when lightning strikes a swimming pool?

    Hi all, In response to the above question, i read somewhere before that when lightning strikes a pool, or the sea, the current will dissipate along the water surface. The current will penetrate only to a small depth into the water. A simple search on Google throws up the simple...
  18. K

    Is laser light polarized or unpolarized?

    Hi all, I understand laser to be monochromatic (i.e. single frequency) and coherent (i.e. all the waves are in phase with each other.) My question is : is laser a form of polarized light too? In other words, can the electric field be in almost all possible plane directions, or is it just...
  19. K

    Charging by induction - Electrons the ONLY mobile charge carriers?

    Hi Doc Al, Thanks for your reply. Its reassuring to hear that coming from you in ur first reply. By insulated, i mean that the 2 spheres are being supported by insulating stands. The metallic surfaces are still exposed for contact. :P
  20. K

    Charging by induction - Electrons the ONLY mobile charge carriers?

    Hi, This is my virgin post. This forum has been a great source of information for the past one year. I am a high school teacher from Singapore. In the study of electrostatics (more specifically induction), we often encounter the scenario below: Two insulated metal spheres touching...
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