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  1. W

    I Heat transfer within a laptop computer from CPU and GPU

    So theoretically would a heatpipe with a higher thermal conductivity result in a lower differential?
  2. W

    I Heat transfer within a laptop computer from CPU and GPU

    Hello all I have a practical question regarding heat transfer within my laptop. My laptop uses a shared-heatpipe design, meaning that my CPU and GPU are connected by a common piece of copper, and then each chip goes off to its own heatsink/fan. While playing games, I was monitoring the...
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    How do you calculate the energy required via torque when...

    The "load" is just my way of saying the force. I understand the integral, I just wasn't sure if it was as easy as dropping in the FrSin[x] into the integral, but I guess it is. Thank you.
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    How do you calculate the energy required via torque when...

    Let's say you have a lever arm connected to a load at the end. But the load is attached to a hinge, so no matter where the lever arm is, the load is always pointing down. I know that Energy = [integral] tau d_phi, but does that only work if the angle b/w arm and load is constant? What if the...
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    How does the Beer Lambert law work at non-normal incidences?

    Okay, so I calculated Rp+Rs / 2, and I got 93% reflectivity, but that doesn't take into account the thickness of the film. I think it's more appropriate as a way to model a thick film where practically nothing makes it through the aluminum film. EDIT: Or is it just impossible, regardless of...
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    How does the Beer Lambert law work at non-normal incidences?

    Thanks Dr Du. Since my light source is going to be unpolarized, the total reflectance is going to be (Rs+Rp)/2. Since both Rs and Rp are dependent on n2, would I just use the real index of refraction to calculate the amount reflected, and then when calculating what is attenuated, use the...
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    How does the Beer Lambert law work at non-normal incidences?

    I want to calculate the intensity of a transmitted wave in a medium, but not at normal incidence. I want to consider the case of 45 degrees. What proportion of the intensity of the wave is lost by reflection? Specifically I am looking at a the reflection off of a thin film of aluminum...
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    Have you ever heard of the physicist Alex Abastian (sp?)

    I'm not sure how it's spelled, Abastian, Ebastian, etc. He died recently, probably within the past year or two.
  9. W

    Measuring the electron mobility of a molecule

    What I have is a layer of Indium Tin Oxide as the anode, a molecule in between, and gold as the cathode. When I run the IV curve of it, it isnt a linear relationship. The closest way I can approximate the behavior is like sqrt(x) or 1-e^(-x). the slope is constantly changing, so I don't know...
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    Measuring the electron mobility of a molecule

    Hello PF Let's say I have a device with three layers, A, B, and C, where layers A and C are the anode and cathode. I can measure the IV curves from that device easily. Now lets say I added a fourth layer, D, in between A and B. Layer D interacts with layer B such that it increases it's...
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    Completely dissolving a gas into a liquid

    Hmmm, then what would be the best way to maximize the amount dissolved? I was thinking, if I added a 1 way valve into the system, then it would draw in air consistently as long as the system isnt at atmosphere. So if anything happened where the pressure of the soda wasn't at atmosphere, the 1...
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    Completely dissolving a gas into a liquid

    Ok, I'll try to clarify. (see attached pic) Let's say I want to re-carbonate soda that's gone flat. I would put soda in a vessel which will allow CO2 to pass through it. And then the CO2 just flows through the soda again and again until its dissolved as much as possible. If I cool down the...
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    Completely dissolving a gas into a liquid

    Hello PF I want to dissolve a gas in a liquid. I figured I could create a closed loop vacuum system. I introduce gas into the lines at atmospheric pressure, and then close off the lines, so the intake and exhaust of the vacuum pump are connected. Then I turn the pump on and the gas just...
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    What would cause sudden change in evaporation chamber behavior?

    I actually figured out the problem. The electrodes were too tight when securing the evaporator boat. I don't know why this happens, I'd figure better electrical contact would mean better performance, but no. I loosened them significantly to the point where I can still shimmy the boat around...
  15. W

    What would cause sudden change in evaporation chamber behavior?

    Hello all, I use an evaporation chamber at my lab every day. Basically, put some substance in the chamber, close it, bring it down to vacuum, and pump enough current through it to vaporize it where it deposits on a substrate. I've been using 175A to create a deposition rate of about 1...
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    Epicyclic motion and precession

    Imagine I am standing but not moving forward/backward, but I am rotating my body about my own axis. Now imagine if I moved in a circular path as I was spinning on my own axis. Is this considered to be precessing (assuming the axis of rotations are always in the z direction)? My friend...
  17. W

    Problems charging a lead-acid battery

    Yeah I think I've come to terms with this stopping in it's tracks at this points. Thanks to everyone and their help, I appreciate it.
  18. W

    Problems charging a lead-acid battery

    Thank you for the prompt response Dave. I had tried what tfr000 had suggested, where I set the voltage to 14.5, then shorted the outputs and set the current limit to 1.5A. However when I turned it on it did what I mentioned in my first post. It starts out drawing only about 150mA, and it will...
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    Problems charging a lead-acid battery

    Hello Dave, sorry for the late reply. I checked the battery. All that it says, aside from things like "Do not dispose of in fire", etc, is 12 VDC Sealed lead-acid battery 5 Ah. It also mentions that during charging, the amount of initial current should not exceed 1.5 A.
  20. W

    Problems charging a lead-acid battery

    I was wondering if there would be any harm in leaving it running at 3A, but when I first tried it out, after about 10 seconds, I could hear some unnerving sounds coming from the battery, so I switched it off.
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    Problems charging a lead-acid battery

    Thank you sir, I appreciate it.
  22. W

    Problems charging a lead-acid battery

    I don't have the battery or resistor in front of me, so I don't know it, but I can get back to you on that. But the resistor was several kOhms and 1 Watt. But it is a small LA battery probably used to start a motorcycle. On the battery, it lists the charging voltage as anywhere from 13.8-14.5...
  23. W

    Problems charging a lead-acid battery

    Hello guys, I have a problem charging a lead-acid battery. I have a 0-30V 0-3A power supply. If I hook up the power supply directly to the battery (with a resistor and/or diode) and set the voltage to an appropriate level, the LA battery will only draw about 150 mA. After a few minutes...
  24. W

    The construction of half silvered mirrors

    Hello guys, I have a question about the construction of half silvered mirrors. I read that they are created using aluminum vapor (so some sort of vapor deposition process?). And I read that the thickness of the aluminum coating can affect the reflectance and transmittance properties...
  25. W

    What will happen with this scale and submerged objects

    Ok, I see, but the buoyancy of the ping pong ball doesn't play any role?
  26. W

    What will happen with this scale and submerged objects

    Homework Statement Hello all, I saw a picture today of a physics problem which is really a head scratcher in my opinion. See the attached photo. You have two columns of water on a scale. In the left column, you have a ping pong ball, attached by a string to the bottom of the container...
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    Gas consumption to overcome drag force

    But how would the volumetric flow rate factor into miles/MJ? VFR would give me m^3 /s or gallons/s
  28. W

    Gas consumption to overcome drag force

    Homework Statement A car moving with speed v is subject to a drag force F_{d}=0.5\rho A c_{d}v^{2}, where \rho is the density of air (1.25 kg/m^{3} at STP), A is the cross sectional area of the car, and c_{d} is the drag coefficient. A Honda Civic has A=1.9 m^{2} and c_{d}=0.36. Assuming...
  29. W

    Confused about the sizes of atomic particles

    Awesome, thanks for the replies gents, I understand it much better now.
  30. W

    Confused about the sizes of atomic particles

    Thanks for the reply. I have taken modern and quantum physics, and I am familiar with wave functions, but the functions we worked with only dealt with the probability of it being at a certain point R away from the nucleus, or it's expectation value, not the radius of the electron itself.
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