What is Transmission: Definition and 748 Discussions

A transmission is a machine in a power transmission system, which provides controlled application of power. Often the term 5-speed transmission refers simply to the gearbox, that uses gears and gear trains to provide speed and torque conversions from a rotating power source to another device.The term transmission properly refers to the whole drivetrain, including clutch, gearbox, prop shaft (for rear-wheel drive vehicles), differential, and final drive shafts. In America the term is sometimes used in casual speech to refer more specifically to the gearbox alone, and detailed usage differs.
The most common use is in motor vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a relatively high rotational speed, which is inappropriate for starting, stopping, and slower travel. The transmission reduces the higher engine speed to the slower wheel speed, increasing torque in the process. Transmissions are also used on pedal bicycles, fixed machines, and where different rotational speeds and torques are adapted.
Often, a transmission has multiple gear ratios (or simply "gears") with the ability to switch between them as the speed varies. This switching may be done manually (by the operator) or automatically (by a control unit). Directional (forward and reverse) control may also be provided. Single-ratio transmissions also exist, which simply change the speed and torque (and sometimes direction) of motor output.
In motor vehicles, the transmission generally is connected to the engine crankshaft via a flywheel or clutch or fluid coupling, partly because internal combustion engines cannot run below a particular speed. The output of the transmission is transmitted via the driveshaft to one or more differentials, which drive the wheels. While a differential may also provide gear reduction, its primary purpose is to permit the wheels at either end of an axle to rotate at different speeds (essential to avoid wheel slippage on turns) as it changes the direction of rotation.
Conventional gear/belt transmissions are not the only mechanism for speed/torque adaptation. Alternative mechanisms include torque converters and power transformation (e.g. diesel-electric transmission and hydraulic drive system). Hybrid configurations also exist. Automatic transmissions use a valve body to shift gears using fluid pressures in response to engine RPM, speed, and throttle input.

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  1. bhobba

    New High Efficiency Power Lines

    I read an interesting article on progress in making transmission lines more efficient: https://reneweconomy.com.au/super-cheap-transmission-upgrades-could-double-capacity-and-open-floodgates-for-renewables/ While, of course, we do not discuss politics here, this new technology has many...
  2. L

    Power Plant Schematic

    A power generation plant converts chemical (or nuclear) energy into electrical energy. This energy is then sent out via conductive transmission line. What would be a simple schematic for this process? That is, if we liken it to a battery, then the positive pole would be the high voltage...
  3. MR v

    Measure the transmission curve and wavelengths of colored mineral glass

    hi , I want to measure the transmission curve and wavelengths of colored mineral glass , which is the simplest way or which instrument can I use ? thanks
  4. Juanda

    Auto/Motor Honda NT700V Deauville motorcycle maintenence: Drive shaft

    I bought a second-hand Honda NT700V Deauville with 62000 km. I did some basic maintenance (oil, oil filter, and air filter) after the purchase, and it worked more or less OK. At 66000 km a bigger maintenance was due. It was discovered that the drive shaft was obliterated. It's a weird thing...
  5. S

    800 ohm transmission line from Ethernet cable?

    If the 8 pairs in a CAT-5 LAN cable are wired as shown so that their impedances add up, will it work well as an 800 ohm line up to around 30 MHz? .... Or, would I have to slit the plastic sheath and put some separation between the pairs?
  6. I

    Disengagement of a multi plate clutch

    I am a student at a mechanical college, current topic of discussion is multi plate clutches. I understand that the clutch is engaged when the pedal is released, with allows the springs to expand, pushing together the plates, that will transfer the torque in to the drive shaft (if in very brief...
  7. davenn

    AM transmission tower signal rectified in electric arc to generate audio

    This short YT video isnt about the AM rectification, it was about why you dont touch transmitter towers I just noted that the audio of the signal could be heard as the guy was generating an arc Pretty cool ..... cheers Dave
  8. A

    I How Do Helmholtz Coils Affect Electromagnetic Beam Transmission?

    What would the behavior of an electromagnetic beam (transmission) be if directed through a Helmhotz coil? Is there a different result with a 4 or 6 coil configuration (all orthogonal)? Is there a direct response depending of frequency of the EM transmission (10kHz - 10 GHz) and current being...
  9. LarryS

    I Transmission Line EM Wave vs EM Wave in Free Space

    According to Maxwell’s Equations, the speed an EM plane wave in free space, far from its source, is determined by the electric constant, ε0, and the magnetic constant, μ0, such that c = 1/√( ε0 μ0). The units of ε0 are capacitance per unit length and the units of μ0 are inductance per unit...
  10. M

    Long distance electrical transmission efficiency

    TL;DR Summary: Just need help with verification of data submitte 1 of 94 Efficiency distance over 3000 km +, plus Temperature over that distance 1-inch amorphous magnetic core 0.05 microns graphene 0.10 microns metallic PZT Helical copper wire with 15 mm...
  11. T

    I Are voltage and current waves in transmission lines an artifice?

    The operation of a transmission line is based on the axial propagation of electromagnetic waves between the two line conductors. However, the study of the transmission lines does not focus on E and B waves but on voltage and current waves. It is considered that there are resistance...
  12. phyzguy

    AC Mains Transmission Tower question

    Hi all. Many of you on the forum seem to be very knowledgeable on power transmission. I often notice transmission towers like this on. I know the three large wire groups are the three phases of the AC power, but the towers often have two smaller wires (red circle) on the top. Sometimes they...
  13. stephen8686

    Questions about Circuit Models of Transmission Lines

    This is for my graduate EM Theory class. My background is physics/optics, so I was able to understand when we solved maxwells eqs. for waves propagating between parallel conducting plates, but that lead into the lumped element circuit model of transmission lines which I don't understand. I've...
  14. Samama Fahim

    Limits of Integration in the Transmission Coefficient

    Initially '0' is the upper limit and ##a = \frac{Ze^2}{E}## is the lower limit. With change of variable ##x = \frac{Er}{Ze^2}##, for ##r=0##, ##x=0##, and for ##r=\frac{Ze^2}{E}##, ##x=1##, so 1 should be the lower limit. However, he takes 1 as the upper limit, and without a minus sign. Why is...
  15. N

    GPS receiver data transfer using RF transmission

    Hi all I want to develop a miniature system using GPS receiver, a micro-controller, an RF transmitter and its receiver. The idea is to acquire lat/long of buoy dropped in sea which is equipped with miniature GPS receiver (with associated circuitry) which can send its position (lat/long data) to...
  16. anorlunda

    Automotive Can we bring back the pushbutton transmission?

    I used to be a happy owner of Chrysler cars with pushbutton transmissions. They worked very well. Today, the center console of my car is high demand territory. I resent the excessive console room taken up by the shifter. What prevents reverting to the pushbuttons? Is is the PRNDL...
  17. L

    B Quantum Entanglement information transmission idea to knock down....

    I work in IT and am a layman in the quantum world. I have obviously misunderstood something in my amateur reading of quantum, but if someone could explain my mistake in the above scenario it might be very insightful for me! Forgive me if the terminology is not correct - or if indeed lay folks'...
  18. mfb

    History of droplets vs. aerosol transmission

    I found this interesting article: The 60-Year-Old Scientific Screwup That Helped Covid Kill It discusses why the initial COVID recommendations were focused on 2 meters distance, hand washing but not much else, and how indoor transmission over larger distances was overlooked initially (largely...
  19. A

    How transmission lines deliver (established?) power from generator

    Hello: I'm confused about transmission lines. According to Faraday's Law, what's induced is an emf that depends on how fast the coils spin, or whatever equivalent to a simple model seen on Physics textbooks. Power, however, is then assumed constant when talking about the power loss due to...
  20. ergospherical

    Resonance in transmission lines

    I've calculated the relationships between the input impedance, line impedance and terminal impedance for a mismatched transmission line (parallel-wire type and of length ##l##). I'm now asked to consider the case where "the source [an oscillator] is in resonance with the line". What exactly does...
  21. abdulbadii

    Used/old transmission fluid should be useful for something else?

    Can a used/old transmission fluid be as a penetrating oil constituent along with acetone 100%, common lubricating oil or grease, etc ?
  22. M

    I Transmission through flow cell using small-angle x-ray scattering

    Hello, I plan to run an experiment using SAXS for in-situ solution phase reaction analysis. We will use a glass micro-fluidic chip due to experimental limitation reasons. I am looking for the optimal path length for these channels (fluid channel depth). My understanding is that we need to...
  23. C

    Looking for help with interpretation of FTIR transmission plot

    I've had an oil sample analysed by 2 separate labs; one of the labs came back with the analysis stating large amount of contamination with element X (sorry, I won't prejudice any responses with the element name for now). Unfortunately one lab used transmission FTIR and the other used absorbtion...
  24. S

    Power lost during transmission

    The current in transmission cables = 20 MW / 240 kV = 250 / 3 A Power loss in cables =(250/3)2 x 20 x 103 = 139 MW , which is not possible Where is my mistake? Thanks
  25. dlgoff

    Underground transmission power lines

    @anorlunda suggested I start a new thread about this: See: https://www.physicsforums.com/threads/grim-day-on-the-texas-power-grid.999764/post-6521013
  26. baby_1

    Complex Reflection and Transmission Coefficient in oblique incidence

    Hello, Something has made me confused after studying the Snell equations these days. Regarding the Balanis Advanced engineering electromagnetic( the pages have been attached), and based on that the reflection and transmission coefficient can be complex I need to rewrite the (5-23a) again...
  27. B

    Light Transmission Measurements: What Else Can You Find?

    If you measure the light transmission over time of the human thumb you can get the heart rate. Is there another thing you can get by using light transmission ? like the Heart rate? can you find bacteria in water using light transmission ?is light transmission measurement even the right word ?
  28. L

    Engineering Give examples of mechanical power transmission failure and solutions for a car

    just want check if i got this right. is there anything i can improve or add on this example i have? Cause and why. A cause could be bending or twisting of the prop shaft due to high torque. High torque causes high angle of twist and torsion. The high torque cause high shear stress...
  29. L

    Transmission line with 2x termination

    Trying to work out the match for a transmission line with 2x termination. Like the one here: https://ibb.co/p4dY7pF V1=1 R1=R2=T1=T2=50, V1 sees R1 and T1. So it is divided to half. Now you have 0.5V source with a 50 Ohms series impedance(T1) looking into a load that is a parallel combo of...
  30. H

    Rate of energy dissipated by a power transmission line

    VR = IR = 400 [ 29*10^-6 * 800 * 10^3 ] = 9280 P = IV = 400*9280 = 3.7 MW I was able to calculate the correct answer from the above, but why can't I use the equation P= V^2 / R?
  31. Wrichik Basu

    COVID Enough reasons to believe in airborne transmission of SARS-CoV-2?

    This comment, entitled "Ten scientific reasons in support of airborne transmission of SARS-CoV-2", was published in The Lancet. Link: https://doi.org/10.1016/S0140-6736(21)00869-2 I am not a student in biology, and don't stay up to date on latest research. Hence, the question from a layman's...
  32. P

    A Transmission Line in Accelerating Frame: Energy Conservation Puzzle

    While I believe I have an answer to this problem, I think it's an interesting one and counter-intuitive. I think it might spark some interesting discussions. The bow of a Born rigid accelerating spaceship has a proper acceleration of g. There is a transmission line running from the stern to...
  33. F

    Air-Gap & Wireless Power Transmission Efficiency

    Summary:: How does the air-gap affect the efficiency ? For a wireless power transmission system, to what extend does the efficiency and coupling parameters get affected by the distance between the coils? What can be done to increase the power transmission or efficiency regardless of the value...
  34. icesalmon

    Engineering Lattice Diagram for Transmission Line

    The propagation speed of the wave is C/sqrt(9) = up if the length of the transmission line is 2m then every 10ns it will pass through the middle of the transmission line. But the switch in the circuit is opened after 5ns so after the current wave bounces off of the Load for the first time it...
  35. P

    Prove the reflection and transmission coefficients always sum to 1

    Consider polarized light crossing a sharp boundary between two volumes, each of a different but uniform refraction index ##n_1## or ##n_2##. Prove that the sum of the transmission and reflection coefficients of this light ##R+T=1##, where $$R \equiv {I_R \over I_I} = \left( {E_{0_R} \over...
  36. D

    I How viscous forces affect force transmission in hydraulic systems.

    Hi everyone, I have a question that I am struggling and need your help. So I am working on a project which is essentially two syringes, A & B, with different cross-sectional areas, A1 & A2, connected via a tube filled with water. If we assume loss-less system, Pascal's law, the input force...
  37. A

    Torque Balance of Motor and Transmission

    I read this in my college design book, that for a car transmission, if the engine provide T, and the output is RT(ratio x Torque), the difference of (RT-T) must be back on the engine mounting. This example makes sense, I am not questioning that.However, if i have an offset gear drive, like that...
  38. Snoopy1234

    Sound transmission to the brain

    Water antenna Humantenna
  39. Mr_Allod

    EM Wave Reflection and Transmission Between 3 Materials

    Hello there. I set up the problem like this, I have a wave incident from air on the anti-reflective coating consisting of: ##\tilde {\vec E_I} (z,t) = \tilde E_{0_I} e^{i(k_1z- \omega t)} \hat x## ##\tilde {\vec B_I} (z,t) = \frac 1 v \tilde E_{0_I} e^{i(k_1z- \omega t)} \hat y## This wave gets...
  40. A

    Selecting hydraulic motors and a pump for hydrostatic transmission

    So I'm trying to make a GoKart that utilizes a hydraulic drive for the front two wheels and a mechanical driveshaft for the back two wheels but my main questions are selecting the motors and pumps. I just want to clarify a few things since I'm not sure if I did my math right. The max RPM for...
  41. E

    Signal Transmission Using Sound Waves

    Consider the following thought experiment... You are an engineer with a very peculiar assignment. With a mind to reduce the investment of excessive human labor and material waste, you have been asked to build an apparatus similar to an old-fashioned voicepipe. You are asked to ensure that the...
  42. M

    Engineering Voltage pulse sketches for reflection on a lossless transmission line

    Hi, I was recently attempting a question about transmission lines and I don't seem to really understand how the voltages travel through the line. Question: If we send a voltage pulse of amplitude ## V_0 ## through a lossless transmission line, what does the voltage at the output look like when...
  43. LCSphysicist

    Problem with reflection and transmission of waves

    See, to illustrate: Let's suppose there is an incoming wave by x < 0, what is the problem? It will find a bead in the string, so: , x < 0 , x > 0 T and R are the transmitted and reflected coefficients. Now suppose there is another bead in x = L. The problem is what happens 0 < x < L: The...
  44. K

    B Understanding the Friis Transmission Equation

    If we had a transmitter antenna with 40dBi gain, and the same antenna on the receiving end, based on reciprocity, the receiver antenna would be 40dBi too. Assuming a wavelength of 0.1m and transmitted power of 100W over 100m, the received power comes out to be 63W based on this calculator here...
  45. ?

    Reflection and transmission of waves in a medium of nonuniform density

    Hello all, Apologies in advance for the text-wall; this is a rather involved question. I am trying to compute the effective transmission coefficient for a medium of non-uniform refractive index. For simplicity I am assuming the slab has thickness ##d##, that ##n(0)=1##, and that ##n(d)=n##...
  46. Wrichik Basu

    Handling brake failure/stuck accelerator in auto transmission cars

    It's been a year since I was issued my driving licence. I have never driven automatic transmission cars, so my idea about them is very faint. I know that there is no clutch pedal, and one doesn't have to shift gears while driving forward - that's it. Last day, I was watching a TV show where...
  47. K

    AC superconductor transmission

    For underground AC transmission, the line charging current prevents the lines from exceeding 100 km due to the close proximity and high capacitance between the line and ground. If the line was made with superconducting material, I think the same distance limitation applies (assuming same power...
  48. wolfy

    B Quantum Tunneling different individual transmission probabilities

    I have gone through all the videos on Youtube about Quantum Tunneling and became interested in it, so any helpful feedback would be appreciated. Do all the different individual transmission probabilities of electrons, protons, and such remain constant? May I ask what is the "formula" or...
  49. WonderfulWorld

    Long Distance Wireless Power Transmission

    Hi Everyone, I wanted to get the communities take on this. Long distance wireless power transmission. I know that you cannot accomplish this with magnetic fields or with radio waves because the energy falls of with the square of the distance but I have been reading about some unique methods to...