Electric potential difference Definition and 71 Threads
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).
Homework Statement
The drawing shows a uniform electric field that points in the negative y direction; the magnitude of the field is 3000 N/C. Determine the electric potential difference (a) VB - VA between points A and B, (b) VC - VB between points B and C, and (c) VA - VC between points C...
Homework Statement
What is the difference in electric potential between a point midway between the charges and a point 0.05 meters away from the positive charge but along the line between the charges?
Homework Equations
UE = K * (Q1*Q2)/r
The Attempt at a Solution
K = 9.0x109Nm2/C2
UE =...
A solid insulating sphere has radius a = 3.2 meters and total charge Q = 3.6 Coulomb's. Calculate the potential difference between the center of the sphere and a point r = 0.64 meters from the center of the sphere. (A positive answer represents the center is at a lower potential, a negative...
Homework Statement
A charge of -3.00 C is fixed in place. From a horizontal
distance of 0.0450 m, a particle of mass 7.20x10^-3 kg and charge
-8.00 C is fired with an initial speed of 65.0 m/s directly toward the
fixed charge. How far does the particle travel before its speed is zero...
I understand what voltage is in the context of electrostatics, but the definition of circuits seems foggy to me.
The common definition I see is something like "voltage is the amount of work per unit charge to be done on a charge moving from A to B". However, this is usually in the context of...
Homework Statement
I have two large parallel plates that are conducting and separated by 10.0cm. The charges on the plates are uniform and equal in magnitude but opposite in sign. The difference in potential between the two is 500 V.
The first question concerning this is which plate...
Two parallel horizontal plates are 0.4 cm apart in air. An oil droplet of m = 4.9*10^-17 kg is introduced between the plates. If the drop has 2 electronic charges and if there is no air buoyancy, you can hold the droplet motionless between the plates if you keep the potential difference between...
Homework Statement
During a particular thunderstorm, the electric potential difference between a cloud and the ground is Vcloud-Vground = 1.3 X 10^8 V, with the cloud being at the higher potential. What is the change in an electron's electric potential energy when the electron moves from the...
I'm back again this week with a problem:
A particle has a charge of +1.5 Micro Coulombs and moves from point A to point B, a distance of .20 m. The particle experiences a constant electric force, and its motion is along the line of action of the force. The difference between the particle's...
Homework Statement
A proton, initially at rest, is accelerated through an electric potential difference of 500V. What is the speed of the proton?
Homework Equations
V=k(q/r)
Solving for r: r=k(q/v)
v=d/t
known charge of a proton: 1.6E-19C
known value of k: 9E9Nm^2/C2
The...
Homework Statement
Question: an electron with a velocity of 5.0x10^{}6 m/s is injected into a parallel plate apparatus through a hole in the positive plate. it moves across the vacuum between the plates. what would the potential difference have to be in order to stop the electron 25% of the...
Homework Statement
A force of .053 N is required to move a charge of 37 microCoulombs a distance of .25m in an electric field. What is the size of the electric potential difference between the two points?
Homework Equations
?
The Attempt at a Solution
I'm really stuck...
A pair of parallel plates is charged by a 12-V battery. How much work is required to move a particle with a charge of --4.0 microcoulombs (MC) from the positive to the negative plate?
Given that,
Emf = 12 V
q = -4 x 10 -6 C
I have,
Work done (w) = q x V
= -4 x 10 -6 x 12...
Electric Potential Difference...Please HELP!
Homework Statement
What potential difference is needed to accelerate a He+ ion (charge +e, mass 4u) from rest to a speed of 2690000 m/s?
Homework Equations
The Attempt at a Solution
Change in V = Change in K
Change in V = 1/2 mv^2...
Homework Statement
Two parallel plates having charges of equal magnitude but opposite sign are separated by 14.2 cm. Each plate has a surface charge density of 33.3 nC/ m2. A proton is released from rest at the positive plate. Determine the potential difference between the plates...
Homework Statement
One particle has a mass of 3.00 10-3 kg and a charge of +7.50 µC. A second particle has a mass of 6.00 10-3 kg and the same charge. The two particles are initially held in place and then released. The particles fly apart, and when the separation between them is 0.100 m...
Homework Statement
Two charged rods, each with net charge -Qo, are held in place as shown in the diagram below
a) A small test charge -qo travels from point X toi point Y along the circular arc shown.
i. Draw an arrow at each point (X and Y) to show the direction of the electric force on...
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...
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...
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...
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...