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 Where a real ground connection has a significant resistance, the approximation of zero potential is no longer valid.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.
A 3.0-kg ball, which is dropped, strikes the ground with a velocity of 16.0 m/s and rebounds with a velocity of -12.0 m/s. What is the change in momentum?
Hi all,
I am wondering about heat pumps, not necessarily ground source heat pump.
What percentage of heat is taken from the ground?
My understanding was that 100% of the heat is taken from the ground but it costs 25% (if COP of 4) in electrical energy (running the compressor) to...
Homework Statement
A box whose mass is 4kg is at rest on the floor. It is then lifted to a height of 2m by a constant a constant force F and then released. At this point the box has upward velocity of 5m/s. Do not use Newton's laws of motion to solve this problem.
A. Find magnitude of the...
Are there any theories based upon Dark Matter (DM) being a precursor or sublayer or ground state to Observable Matter (OM)? Pre-Big Bang? Galaxy distribution linked to DM tendril intersections is consistent with DM providing a pre-existing structure.
Any theories based upon DM interactions...
Homework Statement
A 16-kg sled is being pulled along the horizontal snow-covered
ground by a horizontal force of 24 N. Starting from rest, the sled attains
a speed of 2.0 m/s in 8.0 m. Find the coefficient of kinetic friction
between the runners of the sled and the snow.
Homework...
Not a literal twist! It's just a bit more complex.
Homework Statement
A ball is to be shot from level ground toward a wall at a distance "x". I am given the graph of the y component of velocity just as it would reach the wall, as a function of that distance x(m). Here's the equation of the...
Homework Statement
A ball is thrown vertically upward from a window at 10m/s. It hits the ground 5.0 seconds later. What is the height of the window from the ground?
Given
Vi = 10 m/s
Vf = 0
Δt = 5.0 m/s
Δa = -9.8 m/s^2
Find
Δd(w-g) = ?Homework Equations
Δd = Vi(Δt) + Δa(Δt)^2
And the...
Homework Statement
An atom of mass M decays from an excited state to the ground state with a change in mass of ΔM<<M. In the decay process, the atom releases a photon. Use the laws of energy and momentum to determine the energy of the photon, assuming the atom decays from rest.
Homework...
Ground State Wave Equation:
ψ0=(a/∏)(1/4)e(-ax2/2)
Prove the Heisenberg Uncertainty principle ≥h(bar)/2 by way of expectation values.
First I found <x>=0 because it was an odd function
then I found <Px>=0 because it was an odd function
Then <x2>=∫(a/∏)(1/2)x2e(-ax2)/2dx=1/2a by way of...
Hey! :smile: Was discussing with my friends back then about the interesting usage of physics in daily life when we suddenly had some interesting ideas that would be exciting to experiment on.
One of the ideas we had was to calculate the distance and velocity of a flying airplane without...
I hope this is a coherent question: Solving the Schrödinger equation for energy eigenvalues for a harmonic oscillator leads to the ground state of the energy for a particle being ω/2. What is the experimental evidence that this is, in fact, the lowest achievable energy and that zero energy is...
1.Homework Statement
A child pulls a wagon with a constant force of 30 N. How much work is done in moving the wagon 100 m if the handle makes an angle of 30* with the ground?
Homework Equations
Brown = Vector
W=fd
a2+b2=c2
cosθ= Adjacent/Hypotenuse
sinθ= Opposite/Hypotenuse...
Homework Statement
The deuteron ground state is made up of l = 0 and l = 2 states;
a)Show this mixture cannot be an eigenstate of a central potential Hamiltonian
b)Using first-order time independent perturbation theory, argue the potential must contain a term proportional to some combination of...
Homework Statement
3) A projectile is launched with speed v₀ at an angle α₀ above the horizontal. The launch point is a height H above the ground. Ignore air resistance.
(a.) Find the horizontal velocity of the projectile.
(b.) Find the time for projectile to reach its maximum height...
Homework Statement
A projectile is fired from ground level with an initial velocity of 50 m/s and an initial angle of 37°. Assuming g = 9.8 m/s^2, find:
a) the projectiles total time of flight.
b) the maximum height attained
c) the total horizontal distance traveled
d) the final horizontal...
Homework Statement
A good estimate for the volume of a particular hot air balloon is 2800 m3. Suppose the total load (passengers, fuel, balloon fabric, etc.) on a hot air balloon is 724 kg. In preparing to launch, the pilot heats the air inside to an average temperature of 210 oC, giving it...
Homework Statement
The height of a helicopter above the ground is given by h = 2.55t^3, where h is in meters and t is in seconds. At t = 1.65 s, the helicopter releases a small mailbag. How long after its release does the mailbag reach the ground?
Homework Equations
The above equation...
Are there any points along its path at which the velocity and acceleration vectors are perpendicular? Parallel? Also, if a ball is thrown directly upward, wouldn't it fall directly back down?
Homework Equations
The Attempt at a Solution
Homework Statement
I have the following circuit:
The problem states to give arbitrary values to the resistors, and to find the voltage at Vout with respect to the ground, which I named Vx.
Homework Equations
The Attempt at a Solution
I assume that the voltage at Vx is...
Hello Everyone!
I have a question regarding a Quantum problem I am trying to solve in L. Brown's Quantum Field Theory book, Chapter 1, Problem 4.f.
Homework Statement
I have a question which asks me to compute [p][/n], i.e. the probability that the ground state (n=0) is brought to the...
In its ground state, an atom has no net electric dipole momentum ,but it can have a nonzero angular momentum.
Is this a spontaneous symmetry breaking?
why the ground state is not of zero angular momentum?
Homework Statement
If we are simply standing on the ground will our normal force be always equal to our weight besides when we are jumping or when we land on the ground from a fall?
When we are in an elevator, will the normal downwards force on the floor be of our weight (cancelling out our...
Homework Statement
A hot-air balloonist, rising vertically with a constant velocity of magnitude v = 5.00m/s , releases a sandbag at an instant when the balloon is a height v = 40.0m above the ground . After it is released, the sandbag is in free fall.
A: Compute the position and velocity of...
Hello all, I'm new to this forum. I have a scenario that I don't quite understand with my oscilloscope, a tektronix 2246. I'm using it to see the waveform of a square wave frequency generator circuit. The circuit basically has two stages: The first is a 555 timer astable oscillator circuit...
Homework Statement
There are 2 objects both with mass 0.50 kg which are dropped from rest at height h. One is dropped on Earth and experiences air resistance and one is dropped on moon and experiences no air resistance. The gravitational acceleration on Earth is 9.8 and on moon it is 1.6...
Is it possible to construct a portable ground using an positively charged electret?
I think it would be useful to a have an electrical ground that you can move with you anywhere, so that way no matter how powerful a device is, you could use it on the go without risking electrocution.
Is it...
Grounds are always present. Even in a dual supply circuit with +15v/-15v power supply we still need a ground. The question is WHY?
This question is raised in my mind especially because, battery powered circuits do not have a ground. You may say that we need all voltages with a reference point...
Homework Statement
The two objects are dropped from 60 m height. One is dropped having an initial velocity of 20m/s and another with 15 m/s. What is the distance of the objects when the first one hits the ground if there is no air resistance.
Homework Equations
The Attempt at a...
Homework Statement
A plane mirror made of a very thin piece of glass lies flat on the ground. As shown in the following figure, one end of the mirror is 2.1 m from you and the other end is 35 m from a nearby tree. You are 1.6 m tall, and the mirror has a length L. The mirror is arranged so...
Can anyone help me develop some insight as to what positive and negative voltage means?
I've heard of the analogy to water flowing where amps are viewed as units of water flowing through a certain point per unit time and volts are viewed as how high the water is flowing downwards to the...
Devon's bike has wheels that are 27 inches in diameter. After the front wheel picks up a tack, Devon rolls another 100 feet and stops. How far above the ground is the tack?
I did all my work carefully but the answer seems wierd.
circumference of tire :84.78 inches
total distance traveled is...
I'm currently preparing for a classical prelim and am concerned that this problem may not be correct. I'm second guessing myself due to the hint given in the problem, which I did not use. Any help is more than appreciated. A picture of the pendulum is included.
Homework Statement
A...
Say two girls spin a jump rope, of length ∏ meters, so that the only nodes are where the girls hold the rope, ψ= sin(x)exp(iω_1t) (actually there are no nodes at the girls hands as where they hold the rope goes in a smallish circle). Now instruct the girls how to shake the rope so as to most...
What forces keep clouds up in the sky?
It seems to me that they are somewhat close to the ground but yet they always hang at about the same altitude. It looks like they are being held up by something on the bottom since the bottoms of the clouds are flat. But they don't spill out all over...
I have an mp3 player in my car and i think it is having a ground loop issue. Whenever I plug it into my cig. lighter, I could hear a whining noise. The whining noise's pitch is proportional to the engine's RPM. I'm trying to fix and understand the problem because my background is electrical...
I have having difficulty understanding why the ground state configuration of helium has a wavefunction that is the product of two hydrogenic 1s wavefunctions and the spin eigenstate of a singlet state.
Firstly, why is the space wavefcn hydrogenic,
and secondly, why is the spin wavefcn a...
Homework Statement
The problem is from Ashcroft&Mermin, Ch32, #2(a). (This is for self-study, not coursework.)
The mean energy of a two-electron system with Hamiltonian
\mathcal{H} = -\frac{\hbar^2}{2m}(∇_1^2 + ∇_2^2) + V(r_1, r_2)
in the state ψ can be written (after an integration by...
Homework Statement
A particle of mass (m) moves in the one-dimensional potential
V(x) = V0 0 ≤ x ≤ a
= ∞ otherwise
Wave function of the particle is ψ(x,t) = C sin (\frac{x\pi}{a}exp[-iωt]
Determine V0
Homework Equations
Schrödinger's Equations...
By means of an antenna circuit tuned to 7.8hz (earth's resonant frequency). Orrrr an Earth battery? I'm not quite sure how those work exactly but can they be tuned?
Edit:
Earth battery (or Earth Return) was something discovered by Alexander Bain, he got about 1 volt from the ground by placing 2...
We have jack in our lab that is suppose to be connected to ground, but the building is old, and we are not sure if we can trust that it is actually connected to ground. Is there a way to test the ground? If so, what is that way?
Dr. Erzaask
Quantum field theory predicts a value for the cosmological constant that is 123 orders of magnitude larger than the observed value (if one assumes the Standard Model to be correct up to the Planck scale of 10^19 GeV)! To theoretically predict the value of the cosmological constant, one must, I...
I'm quite confused about impact force and weight, as well as momentum. Assuming someone were to fall from a 5-story building, about 20 m, how would you calculate the force upon impact? I know it involves momentum, but I can't quite grasp it.
Also, if someone fell from the building, but instead...
A stone is dropped from the roof of a building; 1.50 s after that, a second stone is thrown straight down with an initial speed of 24.0 m/s , and the two stones land at the same time.
How long did it take the first stone to reach the ground?
V=Vo+aT
I plugged 1.5 s for time, 9.8...
I explained to myself that I don't fall through the ground due to electrons repelling. Using classical electrostatic repulsion.
Once in a while I hear it explained through Pauli's exclusion principle (PEP).
Do we need PEP to explain this, or is classical electrostatics enough?
Hello! This problem has been driving me crazy all week long, and now I am down to the last few hours before the assignment is due. Any help would be greatly appreciated!
Homework Statement
An average person can reach a maximum height of about 60cm when jumping straight up from a crouched...
Homework Statement
In a hydrogenlike ion with atomic number Z, the energies of the allowed states are given by
E(n) = (-13.6eV) (Z^2/n^2)
What is the wavelength asociated with the transition between first excited state and ground state of hydrogen-like helium? (He+)
Homework...
Homework Statement
Consider a quantum mechanical particle moving in a potential V(x) = 1/2mω2x2. When this particle is in
the state of lowest energy,
A: it has zero energy
B: is located at x = 0
C: has a vanishing wavefunction
D: none of the above
Homework Equations
The...
Hi All!
I am trying to build a modular addition to a spectrophotometer (it needs to be mobile and easily removed) thus I have decided to base my design around an Arduino.
My application requires that I power/control a High Power (1W) Infrared LED, and read off temperature measurements from...
Let's say I had a very large circle of wire, and I introduced a charge to it (with the positive terminal on one end of the circle directly opposite the ground). What would happen if before the charge reached the ground I moved it to the other side with a relay, and kept doing this for an...