What is Junction: Definition and 223 Discussions

A junction, in the context of rail transport, is a place at which two or more rail routes converge or diverge. This implies a physical connection between the tracks of the two routes (assuming they are of the same gauge), provided by points (US: switches) and signalling. Junctions are important for rail systems, their installation into a rail system can expand route capacity, and have a powerful impact upon on-time performance.

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  1. S

    Fermi levels in p-n junction under voltage

    I understand that for a semiconductor p-n junction under zero voltage, the Fermi level is constant throughout the junction because that is the condition for a system in thermodynamic equilibrium. I also understand that p-n junction under applied voltage (forward or reverse) is not a system in...
  2. T

    I want to fabricate a pn junction

    Any idea where I can fabricate a p-n junction of a custom length? I want it to be of a particular length and size, any company that can do it for me? How costly would it be?
  3. K

    PN Junction Question - Current

    I guess my most general question would be: Given a P/N junction. Let's say two circular discs, one P one N. There obviously exists some Vgap, and applying some voltage across it excites the electrons, then it emits light (very basic LED or something). Now, what if you took a piece of wire...
  4. A

    PNP Biploar Junction Transistor Energy Band Diagram

    Homework Statement Consider a PNP Biploar Junction Transistor uniformly doped in each region. Sketch the energy ban ddiagram for the case when the transistor is biased in a)In thermal equilibrium b)biased in the active region c)biased in the cutoff (depletion) region Homework...
  5. H

    Max error without reference junction

    Hi I'm using thermocuple as a temp. sensor, it is inside soldering handle output is 0 mV (tested with digital voltmeter at range 200 mV) at room temperature. I'll amplify that voltage using AD623 I cannot use Ice bath to set ref. junction at 0 deg C. I thought using table (ref junction at 0 deg...
  6. L

    WHY is drift current through a PN junction independent of applied bias voltages?

    I have looked all over in many textbooks and I cannot find a decent explanation of this. Most textbooks simply say that it is independent of applied bias because all of the minority carriers generated by thermal energy within a diffusion length of the depletion region will essentially get swept...
  7. S

    Why Is the Fermi Energy Constant Across a PN Junction at Equilibrium?

    Why is it that when no voltage is applied across the pn junction, the fermi energy is the same for both regions?
  8. A

    Understanding Junction Rule: Slide 10 Explanation

    http://online.physics.uiuc.edu/courses/phys102/fall06/print_files/lect06_handout.ppt#10 Slide 10 How come the sign for R3 is not the opposite, shouldn't the postive charge be carried from E2 up to R3 making it + then -
  9. J

    PN Junction Diode: Phi, Va & 0.7V Drop Explained

    For a PN junction diode, the total potential across the semiconductor equals the built-in potential minus the applied voltage. Phi = Phi(built-in)-Va(voltage applied) My question is what happens when the Va exceeds the Phi(built-in)? Will the Phi = negative? But how come they always...
  10. M

    Understanding PN Junction Diodes: Vbi & Measuring Voltage

    During the processing of a PN junction diode when the Ptype material and the Ntype material are joined together. The holes tend to diffuse from the Ptype material to the Ntype material and conversly the electrons from the Ntype material diffuse from the ntype material to the ptype material...
  11. G

    Reversal Potential & Acetylcholine Receptor: How Action Potentials Occur at NMJ

    the reversal potential is about 0mV, so how does opening the acetylcholine receptor at neuromuscular junctions cause action potentials to occur?
  12. S

    I-V characteristics of a silicon p-n junction diode

    Hello all, I've been tasked with drawing the I-V characteristics of a silicon p-n junction diode and I've managed to do that fine. Now, I've been tasked with showing how this curve will vary with temperature (200-400 deg.c) and by illumination with light of photon energy greater than the...
  13. M

    Step PN Junction - Energy Band Diagram

    A step pn junction diode is made in silicon with the n side having N'D = 2x10^16 cm^-3 and the p side having a net doping of N'A = 5x10^15 cm^-3. 1). Draw to scale the energy band diagram of the junction at equilibrium. 2). Find the built-in voltage, and compare with the value measured off...
  14. I

    Understanding the band profile diagram in a junction

    I am confused here and hope to get help from you physicians..the assistant in the uni could not help me.. when we have a junction between two materials with different fermi levels, for example a metal and a semiconductor, we say the fermi level of the semiconductor gets shifted till it's equal...
  15. S

    Exon-intron junction sequences

    I wonder do the genes have the same exon-intron junction sequences or do they have different junction sequences? I was told that all genes have this general junction sequences of the exon-intron-exon: 5'---exon---A/CG-><-GUPuAGU----intron-----Py12NPyAG-><-G---exon---3' The arrows indicate...
  16. E

    Estimating internal (junction) temperature

    Hello. I use a kind of motion sensor located in a sealed metal enclosure. I perform temperature offset calibrating to this device, using an external temperature sensor (attached to the enclosure). This solves the most of temperature problems except when the temperature gradient is large -...
  17. S

    How can I determine the junction area of a diode?

    Hi Guys! How are u my friends? Well i want to ask u one important thing! Please tell me the way to find out the junction area of a diode Thanks in advance
  18. S

    How is the junction area of each diode calculated in this circuit?

    Hi Guys! My Question is this: Dsign the circuit of the fig: so that Vo= 3V when IL = 0 A AND Vo changes by 40mV per 1mA of load current. the value of R = 4.8Kilo ohms. find the juction area of each diode (assume all four diodes are identical) relative to a diode with 0.7 V drop at 1mA...
  19. 0

    Pn junction problem in diode

    when it comes to pn junction in diode, p and n are doping semiconductors. if P and N semiconductor are contacting each other, some holes in P and some electron in N are combined. that is, they are recombined. this recombination caused the current, very small. I was wondering that...
  20. Mk

    Peltier Junction Heats, Doesn't Cool

    I have a peltier junction rated at 12V and when ran both sides become hot, what's wrong?
  21. P

    Understanding the Physics of Peltier Junctions

    What's the physics behind a Peltier (sp?) Junction. I know what it does, but I'm not quite confident how it works. Paden Roder
  22. Mk

    How much does Pelter Junction cost

    How much does it cost? I'm thinking of buying one for a project. Where would I get one?
  23. S

    Figure-8 crossover junction Physics of

    Hi, Does anyone know about the figure of eight crossover junction. I want to make a model toy where a cylinder is moving around the track completing the figure of eight, similar to model trains. How does one drive this cylinder around and how does it cross over from the circle of the eight to...
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