What is Ground: Definition and 941 Discussions

In electrical engineering, ground or earth is the reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the earth.
Electrical circuits may be connected to ground for several reasons. Exposed conductive parts of electrical equipment are connected to ground, so that failures of internal insulation which create dangerous voltages on the parts which could be a shock hazard will trigger protective mechanisms in the circuit such as fuses or circuit breakers which turn off the power. In electric power distribution systems, a protective earth (PE) conductor is an essential part of the safety provided by the earthing system.
Connection to ground also limits the build-up of static electricity when handling flammable products or electrostatic-sensitive devices. In some telegraph and power transmission circuits, the ground itself can be used as one conductor of the circuit, saving the cost of installing a separate return conductor (see single-wire earth return).
For measurement purposes, the Earth serves as a (reasonably) constant potential reference against which other potentials can be measured. An electrical ground system should have an appropriate current-carrying capability to serve as an adequate zero-voltage reference level. In electronic circuit theory, a "ground" is usually idealized as an infinite source or sink for charge, which can absorb an unlimited amount of current without changing its potential. Where a real ground connection has a significant resistance, the approximation of zero potential is no longer valid. Stray voltages or earth potential rise effects will occur, which may create noise in signals or produce an electric shock hazard if large enough.
The use of the term ground (or earth) is so common in electrical and electronics applications that circuits in portable electronic devices such as cell phones and media players as well as circuits in vehicles may be spoken of as having a "ground" connection without any actual connection to the Earth, despite "common" being a more appropriate term for such a connection. This is usually a large conductor attached to one side of the power supply (such as the "ground plane" on a printed circuit board) which serves as the common return path for current from many different components in the circuit.

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  1. chwala

    Find the velocity of the stone just before it hits the ground

    In my lines i have, ##h(t)=ut+\dfrac{1}{2}at^2## where ##u=0##, with ##a=10##, ##h = \dfrac{1}{2}×10t^2## ....................1 ...also, ##h-14.7 = \dfrac{1}{2}×10 (1.4-t)^2## ..................2 1- 2 gives, ##14.7 = 14t -9.8## ##24.5=14t## ##t=1.75## Therefore, ##v = 10×...
  2. A

    B Force Profile of a Hinged Rod on the Ground

    A rod of length 'L' is hinged at one of its ends and is lying on the ground. A torque 'T' is applied to it at the hinge such that it pushes the rod into the ground. What will be the force profile on the ground since the entire length of the rod touches the ground? Assume the rod is weightless.
  3. D

    AC generator, current and ground

    Hi, Let's say we have a basic AC generator, where a single wire is rotated within two magnets: Due to the electromotive force, a voltage is generated so that Va - Vb = 120V. Let's now ground Vb side directly to earth, while leaving Va still open: We can say that Vb = Vc = 0V and Va...
  4. A

    What does the phrase "Mined to the ground" mean?

    “Every meter, every kilometer costs lives. You can do something really fast, but the field is mined to the ground,” he said. From the link: https://edition.cnn.com/2023/07/01/world/wagner-losses-ukraine-zelensky-prigozhin-intl-hnk/index.html What is the meaning of being mined to the ground? I...
  5. I

    Should the power supply float or be grounded?

    I have read pros and cons for both, but would like to hear what people have to say. I can build a simple power supply for a project that supplies 15v that is isolated from earth ground by using the output from a step-down transformer. I can also put one together that shares earth ground. Which...
  6. Lay1

    Determine the voltage at each point with respect to ground

    This is the figure stated for problem 57.
  7. V

    Flag orientation for a boat observer Vs a ground observer

    I am confused by the question. So, the first thing I am trying to understand is whether the flag direction will be same to a boat observer as to a ground observer. I know that the flag will orient itself in the direction the wind is blowing towards, so the flag should always point in NE...
  8. N

    Earth ground meter Vs Multimeter

    Dear forum please help me with the following understanding: There is (are) such equipment Earth ground testers (https://www.fluke.com/en/products/electrical-testi...) - it is used to measure grounded electrical systems or to measure. Such equipment is having multiple poles that are attached to...
  9. vinicius_linhares

    Analysis of the Ground Function: f(x) with $$f''(\bar{x})=0$$

    If f(x) is the function of the "ground": My first assumption is that in a certain $$\bar{x}$$, $$f''(\bar{x})=0$$, and from that point I will analyse the situation. The object has initial energy $$E_0=\frac{mv^2}{2}+mgf(x),$$ then $$v=\sqrt{\frac{2}{m}}\sqrt{E_0-mgf(x)}.$$ In each point the...
  10. hagopbul

    I Can Ground Penetrating Radar Help Locate Earthquake Survivors?

    Hello : As the news coming from Syria and Turkey about earthquake devastation, is it possible to use ground penetrative radar or sound identification and wave frequency spectrum analysis to locate survivours ? The human sound are in the range of 20 kHz shouldnt we be able to use microphones...
  11. M

    Misc. Looking for help calculating heat transfer for PEX ground loop project

    Looking to build a suitable closed loop water (probably glycol mix) circulation system to prevent livestock water troughs from freezing. I assume that I need to calculate how much heat loss is predicted from the water tank in ambient air (varies, but assume worst case), then what length of heat...
  12. J

    Induced drag of ground effect-vehicle

    Model ground effect-vehicle shape like on picture fly above flat surface like floor sports hall or ice, wing end plates and trailing edge is so close to the ground(1mm) we can assume airlfow under the wing is zero and has stagnation pressure("100% ground effect"). How to calculate induced drag...
  13. babaliaris

    How does Earth Ground "absorb" electric current?

    This is a topic that almost no one can actually explain from what I found on the internet. This answer https://physics.stackexchange.com/questions/74625/does-alternating-current-ac-require-a-complete-circuit/74999#74999 is the closest I found so far. The idea is how the grounded neutral...
  14. Lotto

    Can two objects moving parallel relative to a ground meet?

    I think that yes but how to explain it when someone standing on a ground sees them moving paralell? If I move properly, I can see two cars moving paralell ralative to the ground crashing, while someone on the ground do not see them crashing. Is it consistent?
  15. mathbrain9

    Velocity comparison -- Which thrown mass hits the ground first?

    On the test, I said they hit the ground simultaneously. However, that, in retrospect, doesn't seem to be the correct solution.
  16. R

    "Ground" and "Center Tapped" Power Transformer Secondary in guitar amp

    Hello - thank you for reading this, and thank you in advance to anyone who replies and clarifies the mystery of "ground." I have finally gained a full understanding of how a full-wave rectifier, two-power tube electric guitar amplifier works in a push-pull manner, but one thing remains after I...
  17. G

    Torque to rotate a object on the ground about its own axis

    Hi, I have an object sitting on the ground, with a coefficient of friction (COF) of 0.3. Lets say it is a square block, and will rotate on its central axis. How much torque is required to rotate this block? I am ignoring inertia weights as will be rotating very slowly.I can solve my problem by...
  18. Orodruin

    Insights How Can We Jump When the Ground Does No Work?

    [url="https://www.physicsforums.com/insights/how-can-we-jump-when-the-ground-does-no-work/"]Continue reading...
  19. S

    Help with thrust and HP needed to hover 300 pounds at 30' off the ground

    If i wnat to lift/hover my self up 30ft off the groud (i am 110 pounds) how much HP would i need and how much would i need to lift/hover 300 pounds. Please answer TYSM
  20. R

    Understanding Velocity Addition Laws for People on Train & Ground

    I kind of just made up the questions. I realize this is a basic question but my knowledge of physics is very limited.q1 answer v_left_ball = v_left_ball - v_train v_right_ball = v_right_ball + v_train q2 answer To get the speed from Bob's frame I would use v_Bob = v_Bob + v_Alice To get the...
  21. karush

    MHB 3-42 Where on ground (relative to position of the helicopter

    ok this is out of an old textbook and possibly already posted here so.. A movie stunt woman drops from a helicopter that is 30.0 m above the ground and moving with a constant velocity whose components are 10.0 m/s upward and 15.0 m/s horizontal and toward the south. Ignore air resistance. [a.]...
  22. M

    I Can ground albedo near a highway refract noise upward?

    I live near some highways that are roughly "a couple of miles" away. On some blessed days they are inaudible, and on other days they roar with a low frequency sound that penetrates into every corner of the basement. (If frequency matters, it would be most preferable to refract sound at 20Hz...
  23. M

    Engineering Which side of a transformer secondary to be ground referenced?

    The video is located here. My question, if the secondary side is isolated and the control circuit has no connection to the primary side, why do I have to ground X2 only? This a floating AC system, so why does it matter which side is used as the reference? What will happen if I grounded the X1...
  24. Lay1

    Finding the acceleration of the ball in contact with the ground during bouncing

    the v before hitting the ground immediately=4.85m/s the v after hitting the ground immediately= 3.96m/s I considered the down positive, then v= u+at 3.96= 4.85+ (a*0.16) so a= -5.56m/s*s The answer is 55m/s*s The parts that I don't get are why it must be -3.96 and why that velocity becomes...
  25. Spinnor

    Large flock of birds seems to fly into ground, many dead and injured

    From YouTube search, "flock of birds crashed into the ground", Story that got me to search on YouTube, https://www.wesh.com/article/birds-drop-from-sky-chihuahua/39091334#
  26. G

    To find the angle between the ground and rods in limiting friction

    Could I please ask for help with the following: Here's my diagram: The forces at the hinge (green) are internal forces. For the whole system resolving vertically gives: R1 + R2 = 4W and horizontally gives: F1 = F2 For the rod of weight 3W only, taking moments about B gives: F1 * L *...
  27. Y

    Considering Earth ground vs floating ground in off grid solar

    Context: I'm building an off-grid, 100% solar powered home. I have a 12 kw solar array wired up to a Sol-Ark inverter and a Fortress 18.5 kwh lithium battery. Question: What is the ideal grounding/earthing scheme? Additional context: where I'm building, there is currently no requirement that...
  28. 1

    Using Variational Principle to solve ground state energy

    First I picked an arbitrary state ##|ϕ⟩=C_1|φ_1⟩+C_2|φ_2⟩+C_3|φ_3⟩## and went to use equation 1. Realizing my answer was a mess of constants and not getting me closer to a ground state energy, I abandoned that approach and went with equation two. I proceeded to calculate the following matrix...
  29. W

    A Ground state of the one-dimensional spin-1/2 Ising model

    Hi, I know that the ground state of the spin-1/2 Ising model is the ordered phase (either all spin up or all spin down). But how do I actually go about deriving this from say the one-dimensional spin hamiltonian itself, without having to solve system i.e. finding the partition function? $$...
  30. LCSphysicist

    Rod colliding with the ground (Special relativity question)

    Ok, so basically: There is a frase with a particle moving horizontally with velocity v and a rod parallel to the ground, with rest length L, falling with speed u vertical constant. The rod bounces off on the ground. Describe what happens in the particle frame and find the angle the rod makes...
  31. .Scott

    Atypical demonstration of ground effect

    Here is an interesting YouTube video explaining what happened with the most recent Astra launch. One of five rocket engines failed almost immediately. According to the video, this left the rocket with a thrust-to-weight ratio of 1.00 until the fuel burned off. But it took about 10 seconds...
  32. BigBambu 152-462 MHz

    Automotive chassis ground minus the chassis

    I’ve installed an inverter, 12v to 120vac. The inverter has a post meant for grounding to the vehicle chassis. No chassis or other ground is available in this application for the inverter to recognize. I’ve homebrewed what amounts to half of a large capacitor. There’s just one “plate”, with the...
  33. E

    What does it mean for an object to act as the "ground"?

    they said that Y is acting as the ground, what does it mean?
  34. B

    Impedance/admittance (acoustic) models for outdoor ground and seafloor

    There are some mathematical models (eg Delany-Bazley) to calculate impedance of porous materials and these formulas give complex impedance values as a result. But I could not find any model to be used for seafloor (underwater ground modeling) or I don't know if existing models may be used. I...
  35. S

    Shielding Dirty Electricity Ground Current

    Would using an insulator like rubber tires partly buried in the ground + partly protruding above the land surface to create a continuous perimeter around a piece of land possibly shield the land inside of it from the accumulation of charge on the surface of the Earth which occurs in the vicinity...
  36. S

    Ground currents to detect a civilization?

    In a scenario where explorers are trying to detect an active, perhaps subterranean, civilization, is it plausible that they would use equipment that measures ground currents (i.e. actual electrical currents in the terrain)? With technology that exists today, would we expect to detect a...
  37. G

    Vectors - Aircraft's velocity relative to ground

    I attach my working below - my angle is correct according to mark scheme but magnitude isn't (should be 230). I think it's odd that my resultant velocity on a windy day is larger than velocity in still air, but apparently my angle is correct? I've been told that I've calculated the airspeed it...
  38. V

    Forces on particle in complex motion relative to ground observer

    A table with smooth horizontal surface is fixed in a cabin that rotates with a uniform angular velocity ω in a circular path of radius R. A smooth horizontal groove AB of length L(<<R) is made on the surface of the table. The groove makes an angle θ with the radius OA of the circle in which the...
  39. P

    A Ground Penetrating Radar formula

    I am interested in the physics of ground penetrating radar. 1) Does anyone know where I can find a derivation of the formula in the attached jpg for the energy reflected? K=the dialectic constant. 2) An intuitive explanation of why the dialectic constant is important in determining the energy...
  40. brotherbobby

    Maximum range on ground for an elevated cannon

    I sketch a diagram for the problem and show it to the right. My approach is going to be along the following lines : (1) Use the equation of motion in the ##x## direction to express the total time of flight ##T## as a function of the range and initial angle ##T = T(R, \theta_0)##. (2) Plug this...
  41. P

    Ising equation ground state

    The answer for triangular net is -3NJ, so D=3, although I think that it has two dimensions in spite of every atom having three near neighbours.
  42. PazHeping

    Can a Wing in Ground Effect Racer Be Built for Under $1000 USD?

    Hi All, I am working on a wing in ground effect racer. I’m a glider pilot with an engineering background. I want to create a very small very simple craft that will operate in the ground effect regime. Think pod racer from the Star Wars prequels. Most simply it’s a single wing in back that will...
  43. nduka-san

    Breaking hard ground with motors

    I'm trying to find a motor that would break hard ground what would you recommend, here is my research so far: My research is based on horsepower its bad research but I thought it might apply to a motor since its s also this is under the asumption of a 3 pound hoe people managed to do a lot of...
  44. M

    Engineering Calculate the Capacitance of 3 conductors in the presence of the ground

    Initially, I thought to apply the image charge theorem, but I don't know how to continue. Someone could give me some indication on how to solve the problem? Thank you.
  45. T

    Ball's motion after one bounce off the ground - SUVAT Question (ENGAA 2017)

    Please scroll-down to the end (Question 54): https://www.undergraduate.study.cam.ac.uk/files/publications/engineering_s1_qp_2017.pdf I have also been referring to unofficial worked solutions (http://www.engineeringadmissionsassessment.com/2017-solutions.html), but I didn't understand how it...
  46. R

    Solving for Time to Reach Ground: Calculating Velocity of Sound over 50m

    So I figured that to find how long did the ball take to hit the ground I would have to subtract 6 with the time it took the sound to reach back to the player. My givens are Velocity Intial = 330 m/s, speed of sound Δd = 50m Velocity Final = 0m/s because sound stops when it reaches the ear...
  47. david_nelson

    A EM Penetration Depth Into the Ground

    Hello, I'm wondering about the best EM to penetrate deep into ground and sense/detect what's there. The authors here (https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2005JE002528) are recommending P-band with 430 MHz to probe few meters into the ground of Mars; that's about 70-cm...
  48. Diracobama2181

    I Ground State in Peskin and Schroeder

    In P&S, it is shown that $$e^{-iHT}\ket{0}=e^{-iH_{0}T}\ket{\Omega}\bra{\Omega}\ket{0}+\sum_{n\neq 0}e^{-iE_nT}\ket{n}\bra{n}\ket{0}$$. It is then claimed that by letting $$T\to (\infty(1-i\epsilon)) $$ that the other terms die off much quicker than $$e^{-iE_0T}$$, but my question is why is this...
  49. U

    What Forces Cause an Airbag to Jump When Detonated?

    Let me explain: In the Finnish forum for extremely stupid people like myself, I stumbled on this kind of silly dilemma: You have an airbag, and you put it on the ground, airbag pointing upwards. When you detonate it, it will jump up and fly. What force make it jump? Is it that expanding bag...
  50. dRic2

    Ground state density requirement

    I've been think about it for hours but I'm really out of clue here... The only things I could think of are obvious or useless... Any help would be greatly appreciated.