What is Potential difference: Definition and 699 Discussions
Voltage, electric potential difference, electromotive force (emf), electric pressure or electric tension is the difference in electric potential between two points, which (in a static electric field) is defined as the work needed per unit of charge to move a test charge between the two points. In the International System of Units, the derived unit for voltage (potential difference) is named volt. In SI units, work per unit charge is expressed as joules per coulomb, where 1 volt = 1 joule (of work) per 1 coulomb (of charge). The old SI definition for volt used power and current; starting in 1990, the quantum Hall and Josephson effect were used, and recently (2019) fundamental physical constants have been introduced for the definition of all SI units and derived units. Voltage or electric potential difference is denoted symbolically by ∆V, simplified V, or U, for instance in the context of Ohm's or Kirchhoff's circuit laws.
Electric potential differences between points can be caused physically by electric charge build up or imbalance (eg. well known "static" and electronic capacitor) also by electric current through a magnetic field, and by time-varying magnetic fields (eg. dynamo or generator), or some combination of these three. Additionally on a macroscopic scale potential difference can be caused by electrochemical processes (cells and batteries) and pressure induced piezoelectric effect and heat induced emf across metal junctions. These latter processes at microscopic level have the physical origins previously mentioned. A voltmeter can be used to measure the voltage (or potential difference) between two points in a system; often a common reference potential such as the ground of the system is used as one of the points. A voltage may represent either a source of energy (electromotive force) or lost, used, or stored energy (potential drop).
If you know the potential difference between two power lines, (50 kV) and that the electric field between them is uniform, how would you go about working out the minimum distance they can be separated without discharge occurring between lines?
I've looked at the equations for Coulomb's law...
I am looking for some help on how to apply the law of energy conservation when applied to a voltage difference. Specifically, here is what I am thinking.
If you build a voltage difference on a capacitor, I know it takes energy to build that difference, but once it is there, can the...
I'm trying to find the mass of an unknown ion and I think the equation I'm down to to find the mass only requires me to determine the velocity before I can calculate mass -- but I don't know how.
Could anyone help me out and direct me to an equation(s) that would help me find the velocity of...
I'm having trouble with curcuits, my first problem is that I'm not sure if this is a combination parallel-series curcuit?
For the simple circuit (attached diagram) determine the current through each resistor and the potential difference at the 5 ohm resistor.
I think that the 2 ohm...
I need a little help with this question:
Calculate the work needed to move a 1.5uC test charge from point B to point D. (I have attached the diagram)
The first part of the question required me to find the electric field at the points A, B, C and D. Which I think I figured out ok.
I...
I got this homework and I don't know what formula to use on these problems:
An electron is accelerated across a potential difference of 54V. (a) Find the maximum velocity of the electron. (b) Calculate the deBroglie wavelength of the electron.
Please help!
Kirchoff's law states that, the potential difference along a closed circuit must be ZERO.
Now, let's do a simple question 1.
We have a simple circuit consists of INDUCTOR and Voltage source-->V=V.sin(wt)
At any instant, why must the voltage supplied equal the voltage generated in the...
Here is the question:
A parallel-plate capacitor is made of two circular plates, each with a diameter of .0025m. The plates of this capacitor are separated by a space of .00014m. What is the potential difference between a point midway between the plates and a point that is .00011m from one of...
Point A is at a potential of +220 V, and point B is at a potential of -120 V. An alpha-particle is a helium nucleus that contains two protons and two neutrons; the neutrons are electrically neutral. An alpha-particle starts from rest at A and accelerates toward B. When the alpha-particle arrives...
Can anyone help me with a hint of some sort? I am lost...
A small sphere with mass 1.50 g hangs by a thread between two parallel vertical plates 5.00 cm apart. The plates are insulating and have uniform surface charge densities + and -. The charge on the sphere is q = 8.90 10-6 C. What...
A 4.0g object carries a charge of 20uC. The object is accelerated from rest through a potential difference, and afterward the ball is moving at 2.0 m/s. What is the magnitude of the potential difference?
I know i have to use the law of conservation
Potential_initial + KE_initial =...
Points A (3 m, 2 m) and B (6 m, 6 m) are in a
region where the electric field is uniform and
given by E = Exi + Eyj, where Ex = 3 N/C
and Ey = 2 N/C.
What is the potential difference VA-VB?
Answer in units of V.
I used E(rB-rA)
sqr rt(13) times (sqr rt (72) - sqr rt (13)) = 17.59...
I'm working on the following problem:
The drawing shows four point charges. The value of q is 2.0 µC, and the distance d is 0.74 m. Find the total potential at the location P. Assume that the potential of a point charge is zero at infinity...
Can someone help me to describe the differences between a 12V car battery and a 9V radio battery. They both convert chemical energy into electrical energy, but the car battery has the capacity for much higher currents with similar voltage to the 9V.
Thanks
The problem says that there are two parallel plates having charges of equal magnitude but opposite signs and they are separated by 16cm. Each plate has a surface charge of 31 nc/m2(sorry don't know how to superscript). I need to find the potential difference between the plates.
I thought I...
Magnitude and direction of E
Ok, hear is the question I need to answer, "What is "E" in direction and magnitude at the centre of a square if q=0.1uC." Now my question is about the diagram that is provided I don't know what the values at each of the corners of the square are for, they are simply...
Question: Spark plug in car has electrodes. They are spearated by 0.6mm. To create spark electric field of 3.0x10^6 V/m is needed.
a) What Potential difference is requuired to initiate the ignition.
Possible Answer: Is this just multiply Electric field by the distance between electrodes...
question:
A certain proton needs to have a lamba of 0.0055 x 10^-9m. What potential difference must this proton be accelerated to achieve this wavelength?
what i know:
im assuming that what we need to find in this question is the amount of kinetic enegry needed to achieve such a lambda...
Hello every9one I'm stuck on finding the first part:
A series RLC circuit is driven by an alternating source at a frequency of 380 Hz and an emf amplitude of 90.0 V. The resistance is 20.0 , the capacitance is 12.1 µF, and the inductance is 24.2 mH.
What is the rms potential difference...
There seems to be two different uses of potential difference that either contradict each other, or at the very least make it very confusing. Let me write the three different forms:
Definition: Vf-Vi= -E*d
Differential: dV=-E*dr (Vi=0)
Point Charge: V=E*r (Vf=0)
What is with the different...
Hello everyone, I'm confused, i know the loop rule and the sum of the Potential differences is 0 in a closed circuit but I need to find the Va-Vb of the circuit. Here is the picture: http://www.webassign.net/hrw/hrw7_27-40.gif and here is the info:
the resistances are R1 = 1 , R2 = 2.2 , and...
In this problem I am getting stuck on how to find the potential difference. I don't know where to begin. In a Geiger Counter suppose the radius of the central wire is 145 micrometers and the radius of a hollow cylinder is 1.80 cm. What potential difference between the wire and the cylinder...
Hello forum dwellers :D
I recent have been coming across questions which deal with large arrangements of resistors and in other cases circuits with open switches where the goal is to calculate the potential difference.
These questions have been causing me quite a bit of strife and i was...
A huge 4.0-F capacitor has enough stored energy to heat 2.5 kg of water from 21 degree Celsius to 95 degree Celsius. What is the potential difference across the plates?
What equation am I supposed to use for potential difference?
Is it V = Change in PE / q
V= - W / q...
Electrons in a television set are accelerated through a potential difference of 2.0 kV.
(a) Find the speed of the electrons when they reach the screen. Ignore any relativistic effects.
how to do this i have no idea what formula to use
I'm learning about charge right now and I have no idea how to start this one.. any help is appreciated.
A helium balloon has a charge of q = 5.5 x 10^-8. It rises vertically into the air. d = 600m. from the surface of the Earth to final position A. The electric field that normally exists in...
We have a right circular cone of base radius a and height a with a uniform surface charge sigma. I want to determine the potential difference between the apex of the cone and the center of the base (this cone doesn't have any charge on the base).
My plan of attack for the problem was to...
Here's the problem I am having trouble with, even though i think it should be simple...
Four identical charges (+3.5uC each) are brought from infinity and fixed to a straight line. The charges are located .35m apart. Determine the electric potential energy of the group.
So I've tried...
A battery fully charges a parallel plate air gap capacitor. The battery is removed and the plates are pulled apart. What happens to the potential difference between the plates as they are being separated?
So I guess resistance and I operate over a certain length. So the length is...
Two parallel plates having charges of equal magnitude but opposite sign are separated by .12 m. Each plate has a surface charge density of 36 nC/m^2. Determine the potential difference between the plates.
I have to admit I am at a bit of a loss on how to answer this
(lettings S...
When a potential difference of 162 V is applied to the plates of a parallel-plate capacitor, the plates carry a surface charge density of 33.0 nC/cm^2. What is the spacing between the plates?
>> I'm rather confused with this question. I know that deltaV = Ed and I tried solving for d, but I...
1. Through what potential difference would an electron need to be accelerated for it to achieve a speed of 50.0% of the speed of light, starting from rest? The speed of light is c = 3.00 108 m/s.
>> I'm really not too sure what to do with this problem. I took .50*3.00e8 and got 1.50e8...
I've been thinking while studying physics and came up with the following problem:
A current I, starting at a point A, flows through a resistor with R=25 kΩ, a capacitor with C=4milliF, and an inductor with L=7 Henry to finish in point B. At a time when Q=8 milliC and the current I=0.2...
1. potential difference = voltage?
2. What's the difference between electrical energy and electrical potential energy ?
3. In light bulbs, when the resistance is increased, is it brighter?
4. When voltmeter or ammeter is equipped with the electric circuit, will the light bulb in the circuit...
An electron is accelerated by a potential difference of, say, 100V. How much greater would its final speed be if it were accelerated with four times as much voltage?
Hi I am doing a report on electrostatic force. It involves 2 steel plates which are connected to a 5kV DC power supply and are separated 8cm from each other. A table tennis ball painted in metallic paint (to conduct) is hung from a nylon wire between the two plates. When the power supply is...
A beam of electrons bombards a sample of hydrogen. Through what potential difference must the electrons have been accelerated if the first line of the Balmer series is to be emitted? How does this even begin?
I can frankly say I'm totally confused on how to solve this problem. Here it is:
A think spherical shell of charge Q and uniform volume charge density p is bounded by radii r1 and r1 where r2>r1. WIth V=0 at infinity find the electric potential V as a function of the distance from the centre...
I have a problem from Griffiths Introduction to EM
[problem2.26] A conical surface (an empty ice-cream cone) carries a uniform surface charge <sigma>. The height of the cone is h, and the radius of the top is R. Find the potential difference between points a(the vertex) and b (the center of...
Please assist me with this
The work done to move a 1.0 C charge from point P to Q is 3.0 * 10^-4J. If the charge starts from rest and has 1.0 * 10^-4J of kinetic energy when it reaches point Q, what must the potential difference be between P and Q?
For this would I use
Work done =...
A 3Ohm and a 1.5 ohm resistor are wired in paralles and the combination is wired in series to a 4 ohm resistor and a 10 V emf device. The potential difference on across the 3 ohm resistor is?
I reduced the 2 in parrallel to 1.875 ohms and then addes the 4 ohm, which gave me a total...
Here's my problem:
A parallel-plate air capacitor has a capacitance of 730 picoFarads. The charge on each plate is 2.95 microCoulombs.
a) What is the potential difference between the plates? I used the equation V=Q/C to get 2.4746E-4 V, but this is incorrect.
b)If the charge is kept...
Problem 4.
Given: k_e=8.98755*10^9 nm^2/C^2 and g=9.8 m/s^2.
find the potential differnece between a point infinitely far away and a point 1.4 cm from a proton. Answer in units of V.
Note: I don't know where to start!
Problem 6.
Given: k_e=8.98755*10^9 nm^2/C^2 and g=9.8 m/s^2...
ok, i guess i didnt see this forum ... i posted in another forum my question:
https://www.physicsforums.com/showthread.php?s=&threadid=7593
ok, I am taking engineering physics II ... unfortunately, I am forced to take this as part of my COMPUTER SCIENCE degree ... (why i have no...