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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: 167

EMF is the voltage generated by a battery.

Plot Graph Corresponds

Figure 1.38 shows the intensity of X-rays produced from a source as a function of their energy. With respect to the reference graph shown on the left, one plot corresponds to a decrease in tube current and the other to a decrease in the accelerating voltage (kVp). Explain which plot corresponds to a decrease in which parameter.

Electricity Problems

A step-up transformer has 200 turns in the primary coil and 3000 in the secondary coil. The primary coil sees 90 V. What is the voltage out of the secondary? B. if the secondary current is 2.00 A, what is the primary current? C. What is the power in the primary coil?

Calculating the Maximal Charge

Consider a parallel-plate capacitor having a separation of d=0.1mm and a capacitance of Co=11nF when having a vacuum between its plates. If the region between the plates is now completely filled with 19g of silicone oil, determine the maximum amount of charge that can be placed on the plates before dielectric breakdown occurs.

Problems Involving Propagation of Measurement Error

Please see attachment for problems with appropriate symbol notations. 6. Let I = 1/2 M(R^2 + r^2). What is the equation for sigma_I, if M, R and r are measured quantities? If we require delta_I/I = 0.1%, what is the relative precision for the measurements of M, R and r? (Suppose that R = alpha*r, alpha > 1, and delta_R = delt

Voltage of Terminal Apparatus

The overhead cable supplying an outbuilding from the 230V supply has a resistance of 0.9 ohms. A2kw radiator and a 1500w kettle both rated at 230v are in use at the same time. DETERMINE THE VOLTAGE AT THE TERMINALS OF THIS APPARATUS. What WOULD BE THE VOLTAGE IF A 750w; 240Vwater heater was also switched on?

Calculating the Total Current

3. In a certain installation the following items of equipment are operating at the same time.(i)a 3kw immersion heater (ii) two 100w lamps (iii) one 2kw radiator. All there are rated at 240V the nominal supply voltage at the origin of installation is 5Vless than this. Calculate (a) the total current.

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.

Electricity: Current, Voltage and Resistance

Assign any numbers (with units) to two of them and find the missing third value. For example, assign numbers to Voltage and Resistance and find Current. Or assign numbers to Current and Resistance and find Voltage. Name one famous scientist who contributed to the study of electricity.

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 >

Capacitance Problem

A 11.2 microF capacitor is fully charged across a 12.0 V battery. The capacitor is then disconnected from the battery and connected across an initially uncharged capacitor, C. The resulting voltage across each capacitor is 2.08 V. What is the capacitance C? Please solve and explain problem.

Electrons have been transferred when difference in the plates

A capacitor has a capacitance of 2.32E-8 F. In the charging process, electrons are removed from one plate and placed on the other plate. When the potential difference between the plates is 460 V, how many electrons have been transferred? Please solve and explain problem.

Energy in a Capacitor: Acetylene Gas

Acetylene gas is leaking from a cylinder in the immediate vicinity of an insulated conveyor belt which has built up a charge of 2.0µC. If the conveyor belt has a capacitance of 80pF, is there a danger of the acetylene being ignited? Consider both energy and voltage in your answer.

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

Electrostatics: Capacitance of a spherical capacitor.

A spherical capacitor is formed from two concentric, spherical conducting shells separated by vacuum. The inner sphere has radius 15.0 cm, and the capacitance is 116 pF. 1.) What is the radius of the outer sphere? 2.) If the potential difference between the two spheres is 220 V, what is the magnitude of charge on each sph

Electrostatics: Capacitance of a Cylindrical Capacitor

A capacitor is made from two hollow, coaxial, iron cylinders, one inside the other. The inner cylinder is negatively charged and the outer is positively charged; the magnitude of the charge on each is 10.0 pC. The inner cylinder has a radius of 0.200 mm, the outer one has a radius of 5.40 mm , and the length of each cylinder is

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?

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.

dielectric constant of this glass

A capacitor with air between its plates is charged to 70 V and then disconnected from the battery. When a piece of glass is placed between the plates, the voltage across the capacitor drops to 43 V. What is the dielectric constant of this glass? (Assume the glass completely fills the space between the plates)

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.