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Voltage, also referred to as electrical potential difference, or an electric tension, is the electric potential difference between two points, or the difference in electric potential energy of a unit test charge transported between two points. It is measured in units of electric potential, volts or joules per coulomb. Voltage is equal to the work done per unit charge against a static electric field to move the charge between two points.

A voltage can represent either a source of energy, lost, used or stored energy. A voltmeter is used to measure the voltage between two points in a system. Voltage can be caused by static electric fields by electric current through a magnetic field, by time-varying magnetic fields, or some combination of these.

Similar to mechanical potential energy, the zero of potential can be chosen at any point so the difference in voltage is the quantity which is meaningful. The difference in voltage measured when moving across point A to point B is equal to the work which would have to be done, per unit charge, against the electric field to move the charge from A to B. This voltage between the two ends of the path is the total energy required to move an electric charge along the path divided by the magnitude of the charge. This relationship can be mathematically modeled as the line integral of the electric field and the time rate of change of magnetic field along that path.

Voltage is defined so that negatively charged objects are pulled towards higher voltages, while positively charged objects pull towards lower voltages. This follows the principle that opposites attract. The conventional current in a wire or resistor always flows from higher voltage to lower voltage. It is possible for current to flow from lower voltage to higher voltage, but only when a source of energy is present to push it against the opposing electric field. 

Categories within Voltage

Kirchhoff's Voltage Law

Postings: 36

Kirchhoff's Voltage Law states that the total voltage around a closed loop system must be equal to zero.


Postings: 168

EMF is the voltage generated by a battery.

Solve for Node Voltage; Write KCL and KVL Equations

** Please see the attached graph for further illustration ** Please help with the given questions: a. Using KCL write an equation for the currents I4, I5, I6 at the node point N. b. Express the KCL equation in step above in terms of VRIR and VnIR c. Write a KVL equation for the loop containing V4, VR5, and VR6 d.

A problem determining capacitance & PD across spherical cap

Calculate the capacitance of a spherical shell capacitor given two plates one charged at +Q coulombs at a radius (a) from the center another plate charges at -Q coulombs at a radius (b) from the center and given that: The voltage at a region between the spherical shells is given by V(r) = kQ/r (a >

Magnetic Fields and Forces.

1)/2)/3) I have the Mag field B, the charge q, and the velocity v. To find the force I cross q*v with B. 4)I have the current I, the Mag field B, with the field in the x-z plane. I find the force using B = F/(I*l)? 5)I have the area A, length l, voltage V, resistivity (rho)and Mag field B. R = (rho)*l/A. I can find t

Algebra Based Physics

See the attached file. You are probably familiar with "three-way" light builds, such as 1100/200/300W bulbs which have two filaments. As you turn the switch to its various settings the 100-W filament filament comes on by itself, then the 200-W filament comes on by itself, and then both filaments come on (connected in parallel)

Deriving Telegraph Equations

Could you please show me how to derive the telegraph equations for a loss-less transmission line? Also, please solve this problem with step-by-step calculations. A loss-less transmission line of characteristic impedance Z0 is terminated by a resistive load R. Find an expression for the input impedance of a section of the


The batteries in a portable CD player are recharged by a unit that plugs into a wall socket. Inside the unit is a step-down transformer with a turns ratio of 1:13. The wall socket provides 120 Volts. What voltage does the secondary coil of the transformer provide?

Battery Problem

A battery charger is connected to a dead battery and delivers a current of 6.0 A for 5 hours, keeping the voltage across the battery terminals at 12 V in the process. How much energy is delivered to the battery?

Input and Output Voltage

Show that the output voltage, v_o, of the following circuit (see attached file) is proportional to the derivative of the input voltage v_i. If C = 10^-5 F, what value of R is required if v_o = dv_i/dt Assume the operational amplifier is ideal.

Energy of capacitor

We want to store sufficient energy in a .01-F capacitor to supply 5-hp for 1 hour. To what voltage must the capacitor be charged? (1 hp=745.7 watts). Does this seem to be a practical method for storing this amount of energy? Do you think that an electric automobile based on capacitive energy storage is feasible?

Easy Capacitor Problem

Hi, I am a bit confused with this question. I don't know what I'm doing wrong, but I keep getting the wrong answer. Question: Three capacitors (4.0, 6.0, and 10.0 uF) are connected in series across a 50.0 V battery. Find the voltage across the 4.0 uF capacitor. Answer in Volts

Resistors 2

Problems: See attachment. Please show the formulas used, work done and the answers! Thank you!


1. When electrons move through a metal conductor, a. they move in a straight line through the conductor. b. they move in zigzag patterns because of repeated collisions with the vibrating metal atoms. c. the temperature of the conductor decreases. d. they move at the speed of light in a vacuum.

Diode Current Manipulation - A schottky diode and a pn junction diode have cross sectional areas a=10^-4. The reverse saturation current density of the pn junction diode is 3x10^-8 A/cm^2. The reverse saturation current density of the pn junction diode is 3x10^-12A/cm^2. Determine the forward bias voltage in each diode required to yeild diode currents of 1mA.

A schottky diode and a pn junction diode have cross sectional areas a=10^-4. The reverse saturation current density of the pn junction diode is 3x10^-8 A/cm^2. The reverse saturation current density of the pn junction diode is 3x10^-12A/cm^2. Determine the forward bias voltage in each diode required to yeild diode currents o

Capacitance: What is the distance between the plates?

When a potential difference of 178 V is applied to the plates of a parallel-plate capacitor, the plates carry a surface charge density of 47nC/cm^2. What is the distance between the plates? Answer in units of micrometers.

The problem is to find current density.

Given two plane-parallel electrodes, space d, at voltages 0 and V_0, find the current density if an unlimited supply of electrons at rest is supplied to the lower potential electrode. Neglect collisions.