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 Where a real ground connection has a significant resistance, the approximation of zero potential is no longer valid.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.
Greetings !New to the forums.
Here expanding my concept of what AC Electricity is
My question (correct me if wrong)..
If AC power alternates between +,- at a rate of 60Hertz/second and negative is used as -earth- at the AC generator
If the hot wire touches the ground would happen? (I think...
Hiya, I'm a bit of an intermediate in electronics and I am moving into oscillator territory and am thinking more about "ground" rather than "the negative side of the battery". Obviously, using -ve voltage as ground has some setbacks with dc-ac oscillators as current can only flow if there is a...
New to the forum :)
We were (trying to) discussing this at work the other day. Consider a simple battery powered circuit, with a resistor and an LED. With a battery, current is "chemically produced" in the battery and flows from the positive to the negative pole, passing through the LED...
Notation: ##J^p## - ##J## the total angular momentum, ##p## the parity = ##+## or ## -. ##
Ok so I'm given a diagram of energy levels, all have a ground state of ##0+##, except one which has a ground state of ##1+##.
I'm askeed to indentify which set of energy levels belong to which nucleus...
I have a 3 conductor wire that are all wrapped in a foil shield with wire conductor, for a total of 4 wires.
I am connecting the 3 inside wires to audio left, right, and ground. This is an unbalanced setup, right?
Where/how do I connect the shielding?
Do I connect both sides (i think no)...
Hi Physics Forums!
The ground state electron is the largest negative value, but what does this mean?
Does this mean that kinetic energy is a positive value above zero?
It seems at the ground state, the electron might also have kinetic energy as it is moving around as well as potential...
Homework Statement
A long, straight power line is made from a wire with radius ra = 1.0 cm and carries a line charge density λ = 2.6 μC/m. Assuming there are no other charges present, calculate the potential difference between the surface of the wire and the ground, a distance of rb = 22 m...
Homework Statement
A car has four tires in contact with the ground each of which is inflated to an absolute pressure of 3.1×105Nm^-2. If a person of mass 82 kg gets into the car by how much will the total area of contact between the tyres and the ground increase assuming that the tire pressure...
I have several questions about poles and towers.
a. Does all of transmission towers carries three-phase powers? Is there no transmission towers designated for single-phase?
b. Does all towers are for transmission purposes only? Is there any towers in the world used for distribution instead of...
Hello All,
I am pretty sure that when a nucleus decays via e.c. and goes to the ground state all of the excess energy is released with the emission of the neutrino but was wondering if anyone could confirm/give a reference for this.
Thanks!
Homework Statement
A lunar lander is descending toward the moon's surface. Until the lander reaches the surface, its height above the surface of the moon is given by y(t)=b−ct+dt2, where b = 770m is the initial height of the lander above the surface, c = 62.0m/s , and d = 1.02m/s2 .
Part B...
Dear all,
periodic DFT codes (e.g. VASP) effectively simulate an infinite crystal due to the periodic boundary conditions. However, the energy value that one obtaines at the end of a simulation if finite. Frankly, I'm quite confused right now.
Is the energy to be understood 'per unit cell'...
Homework Statement
Consider a one-dimentional particle in a box with infinite potential walls at x=0 and x=L. Employ the variational method with the trial wave function ΨT(x) = sin(ax+b) and variational parameters a,b>0 to estimate the ground state energy by minimising the expression
E_{T}=...
Homework Statement
Two very long parallel wires 1.0m apart lie on the ground carrying currents 4.0A and 6.0A in the same direction.
How far from the 4. wire are the magnetic field completely cancelled? 1.0m on the other side of the 4.0A wire, what is the magnitude of the magnetic field...
Hi guys!
Suppose there's a particle in a box, initially in its ground state. Suppose that one chooses a system of coordinates such that the potential V(x) is 0 from 0 to L.
Suppose that one suddenly perturbate the system at a particular time so that V(x) becomes 0 from 0 to 2L.
I've calculated...
Homework Statement
A worker lifts a 20.0-kg bucket of concrete from the ground up to the top of a 20.0-m-tall building. The bucket is initially at rest, but is traveling at 4.0 m/s when it reaches the top of the building. What is the minimum amount of work that the worker did in lifting the...
Homework Statement
A body is dropped from a height ##h## with an initial speed 0, reaches the ground with a velocity of 3 km/h. Another body of the same mass was dropped from the same height ##h## with an initial speed 4 km/h. The second body will reach the ground with what velocity ?
Homework...
Hey, I am new to this stuff and was just wondering if someone could help me i need to know what could i use to lift 180lbs about thirty centimetres off the ground, also this device has to be small but still powerful enough to lift the required weight i would appreciate any help i could get.
Thanks
Hello everyone:
I didn't have a complete view of the quantum field theory and cannot understand this question. We now there will always be fluctuation field in the universe which corresponds to the ground state energy 1/2hw of harmonic oscillator.
In the free space, we will use box...
Homework Statement
At t<0 a particle is in the ground state of the potential V(x)= \frac{1}{2} mw^2x^2 . At t=0 the potential is suddenly displaced by an amount x0 to V(x)= \frac{1}{2} mw^2(x-x_0)^2 .
a) What is the probability of the particle being in the ground state; the first excited...
Hello,
I am sure that this question has been answered on here before, but i could not find it. Why is the Earth ground, and where does the electricity go after it gets there. I understand that ground is potentially lower than that of the power company's production etc. but i am curious as...
I have read that, in the early days of the telegraph, two wires were used, but Steinheil, of optics fame, discovered that the circuit could be completed by 'earth return', using the ground as return ...conductor?
That's my question. It's hard to believe that currents strong enough to operate...
Suppose you have the transition amplitude in the presence of a source <q''t''|q't'>_{f}
To extract the ground state, we change the Hamiltonian to H-i\epsilon , because we can write:
$$|q't'>=e^{iHt'} |n><n|q> \rightarrow e^{iE_0t'} |0><0|q>=<0|q>e^{iHt'} |0>=<0|q> |0 t'> $$
where only...
What exactly does it mean when we say that a conductor is grounded? I know it generally means that its potential is zero, but shouldn't the description of potential also give the location of a reference potential?
For instance, if a conducting spherical shell is grounded, if its potential is...
If a voltage source is connected between a ground and a node of unknown potential will it be a super node.
For example would the 5V source be part of a supernode?
From the ground state wave equation the most probable outcome of anyone measurement will be in the center of the atom, at the nucleus. The expectation value is found to be the Bohr radius.
So does this mean that if you measure the position of an electron in a hydrogen atom in the ground state...
Hello,just seeing if someone can help me on here,i have a rc glider measuring 2200 mm on the ground,when in the air it measures about 35mm. Can the the height be calculated from these measurements.
Hi guys, so I've been given a physics question which is black magic to me, so I thought i will ask you for help :) Here is the question:
A pile driver hammer of mass 170kg falls freely through a distance of 6m to strike a pile of mass 410kg and drives it 75mm into the ground. The hammer does...
This may seem like a really basic question (I'm teaching lower school science, and it's not my specialism!), but:
What causes the force which balances gravity, which I think is called "ground reaction force?"
All the descriptions I've seen say that the ground "pushes" up on a stationary...
Homework Statement
A block on a ramp is held by a tension force parallel to the horizontal (not the ramp). If originally the tension force was parallel to the ramp, is the tension force when it was parallel greater, equal, or less than when it is horizontal?
Homework Equations
Trigonometric...
I now understand how the wavefunction graphs look from the hyperphysics: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/hosc5.html.
However, what I fail to understand, is how the wavefunction equation was derived for the 1st excited state, from:
ground_wavelength0 = (a/pi)1/4 e(-ax2/2)...
I am curious, if I were to draw a wave function, would one for ground state and one for excited sate be different? If different, could someone explain how and why? If you could, thanks!
Hello
I been having a "debate" about the load on an engine when going max speed on a lake vs a lesser speed but on an incline..
Here is the basic jist of the discussion...
We are talking about a 150HP snowmobile using a CVT at sea level with low snow conditions that is traveling across the...
Homework Statement
Hello! I am trying to derive the ground state enegry of a hydrogen atom, and have come to
U=\frac{-mk_{0}^{2}Ze^{4}}{n^{2}\hbar^{2}}
Problem is, I know there should e another factor of 2 in the denomenator because I get the ground state energy of hydrogen as being 27.145eV...
Hi guys,
I was working on a formula for the optimal angle for simple point-like projectiles free-falling under a uniform g-field but I got stuck.
after a simple derivation , I obtained the following equation:
R=(vcos(@)/g)(vsin(@)+((vsin(@))^2+2gh)^0.5)
where R , @ , h are respectively the...
I am not talking about Digital circuit ground bounce on PCB.
How do I simulate a Ground bounce for a system that runs on 220V AC.
In real field conditions, the system might be connected to different grounds. How do i replicate this in the lab.
Can I have a SPDT relay between GND1 & GND2...
http://forums.mikeholt.com/showthread.php?t=162981
I thought this would be a link worth sharing here on pf. We seem to have heated arguments going on this forum from time to time about which country has the best electrical system. There are some interesting things to read in the above link...
If I understand it correct during hammerthrow an athlete muscles cause Fcentripetal force on a ball and ball cause reaction Fcentrifual force on athlete.
The athlete also cause Frotation on ball by rotating his body and ball cause Freaction on athlete.
What would happen if athlete would try...
I have often wondered why conventional large wind turbines have evolved with their generators and gearboxes in the nacelle at the top of the tower where they are hard to reach and maintain. Despite this fact, I wish to believe that there may be benefits to a conventional horizontal shaft wind...
I was looking at this graph and wondering what the value of the graph would be before the engines turn on. Should it be 1 g-force or 0 g-force? (the "force" in g-force being a misnomer as it is a measure of acceleration, not force) Below are arguments for each:
Why it should be 1 g-force: We...
I understand that in an electrical outlet, "ground" is wired directly from the outlet to the ground, whereas neutral is wired from all the outlets to the breaker box or wherever in the house, then to the ground, and that neutral is intended to carry current.
That being said, I am confused...
Homework Statement
A ball of mass 1kg is dropped from a height 1m . Estimate how long the ball is in contact with the ground in seconds ?
Details and assumption
Simplify the question by modeling the ball as an ideal spring of spring constant 100Nm .
Take gravitational acceleration if...
Homework Statement
A baseball is hit at ground level. The ball reaches its maximum height above ground level 3.1 s after being hit. Then 2.6 s after reaching its maximum height, the ball barely clears a fence that is 97.2 m from where it was hit. Assume the ground is level.
a) How far...
In a past physics gre question (https://www.physicsforums.com/showthread.php?t=192334), we make use of the idea that the ground state energy of two ions that have spin is when the spins are aligned.
However, the ground state of the helium atom is a spin singlet state, which is a linear combo...
So i am relatively new to electronics and i was wondering, on a circuit there will be grounds but its not an actual wire running into the ground, especially on small circuits in phones and stuff, so how is it grounded and what is used to ground it?
Its attached below. I don't understand how you work out the total head. Can someone explain how you do it? I'm really struggling.
I know how to do the elevation, which is just the height above/below the datum level. And I've checked the solutions as well, it seems like you're supposed to work...
Homework Statement
The Hamiltonian of helium can be expressed as the sum of two hydrogen Hamiltonians and that of the Coulomb interaction of two electrons.
\hat H = \hat H_1 + \hat H_2 + \hat H_{1,2}
The wave function for parahelium (spin = 0) is
\psi(1,2) = \psi_S(r_1, r_2)\dot...
Homework Statement
A 14kg mass is attached to one side of a vertical pulley and an 8kg to the other.
The 14kg mass is 5m above the ground. The 8kg is just resting on the ground. The pulley is frictionless and weightless.
Find the velocity of the 14kg mass just before it hits the...
Why does a voltage tester (that looks like a screwdriver) turn on even when you are "heavily" insulated from the ground e.g. sitting on a wooden chair.
Is it the result of capacitance between the human body and the ground? (i.e. the body and the ground act as conductors, whereas the insulated...