Can anyone out there explain me about electro motive force?

Answer 1

The voltage or electric potential difference across the terminals of a cell when no current is drawn from it. The electromotive force (emf) is the sum of the electric potential differences produced by a separation of charges (electrons or ions) that can occur at each phase boundary (or interface) in the cell. The magnitude of each potential difference depends on the chemical nature of the two contacting phases. Thus, at the interface between two different metals, some electrons will have moved from the metal with a higher free energy of electrons to the metal with a lower free energy of electrons. The resultant charge separation will produce a potential difference, just as charge separation produces a voltage across a capacitor; at equilibrium this exactly opposes further electron flow. Similarly, potential differences can be produced when electrons partition across a metal|solution interface or metal|solid interface, and when ions partition across a solution|membrane|solution interface.

Electromotive force (electricity and magnetism)-

A measure of the strength of a source of electrical energy. The term is often shortened to emf. It is not a force in the usual mechanical sense (and for this reason has sometimes been called electromotance), but it is a conveniently descriptive term for the agency which drives current through an electric circuit. In the simple case of a direct current I (measured in amperes) flowing through a resistor R (in ohms), Ohm's law states that there will be a voltage drop (or potential difference) of V = IR (in volts) across the resistor. To cause this current to flow requires a source with emf (also measured in volts) E = V. More generally, Kirchhoff's voltage law states that the sum of the source emf's taken around any closed path in an electric circuit is equal to the sum of the voltage drops. This is equivalent to the statement that the total emf in a closed circuit is equal to the line integral of the electric field strength around the circuit. See also Electric current; Electric field; Electrical resistance; Ohm's law.

An emf may be steady (direct), as for a battery, or time-varying, as for a charged capacitor discharging through a resistor. Emf's may be generated by a variety of physical, chemical, and biological processes. Some of the more important are:

1. Electrochemical reactions, as used in direct-current (dc) batteries, in which the emf results from the reactions between electrolyte and electrodes. See also Battery; Electrochemistry; Electromotive force (cells).

2. Electromagnetic induction, in which the emf results from a change in the magnetic flux linking the circuit. This finds application in alternating-current rotary generators and transformers, providing the basis for the electricity supply industry. See also Alternating-current generator; Electromagnetic induction; Faraday's law of induction; Transformer.

3. Thermoelectric effects, in which a temperature difference between different parts of a circuit produces an emf. The main use is for the measurement of temperature by means of thermocouples; there are some applications to electric power generation.

4. The photovoltaic effect, in which the absorption of light (or, more generally, electromagnetic radiation) in a semiconductor produces an emf. This is widely used for scientific purposes in radiation detectors and also, increasingly, for the generation of electric power from the Sun's radiation. See also Photovoltaic effect; Radiometry; Solar cell.

5. The piezoelectric effect, in which the application of mechanical stress to certain types of crystal generates an emf. There are applications in sound recording, in ultrasonics, and in various types of measurement transducer. See also Direct-current motor; Kirchhoff's laws of electric circuits; Microphone; Piezoelectricity; Transducer; Ultrasonics..

Answer 2

EMF is a name for the difference in electric potential between two points. It is a measure of the amount of work you would need to do on an electron to move it between those points. It is a path integral of electric field strength times distance, and is the same over all paths between the two points. It is measured in volts.

You can also view a voltage source (say, a 6 volt battery) as the potential to force an electron between those two points, through a resistance. A 12 volt battery has twice the potential to force electrons through resistance, so it would cause twice the current flow through the same resistance.

All practical voltage sources are limited in their capacity to provide a current through a resistance. Reducing the resistance increases the current until the current is near the maximum the source is capable of providing. A battery has its own internal resistance, and the chemical reaction powering it can support an electron stream of limited size.

Answer 3

If we want current, we need to accelerate the electrons in one direction .However the flow for electrons is not that easy as they encounter resistance from the atoms in the cell.
So we need to provide some force so that the electrons can overcome this resistance and we may get current.
This force is measured in terms of e.m.f
It is not a force but work done to send unit current once thru complete circuit thus overcoming the resistance.

The unit so is not N but Volts(=p.d.)

Answer 4

invisible force that pushes electricity! Kinda like, The voltage produced by an electric battery or generator in an electrical circuit or, more precisely, the energy supplied by a source of electric power in driving a unit charge around the circuit. The unit is the volt.

Answer 5

electro motive force or EMF is the potential difference between two plates of a cell. eg. the EMF of simple voltaic cell 1.0 V. It is measured by a voltmeter. It is not a force in reality.

Answer 6

Explain Electromotive Force

Answer 7

defined as the amount of energy gained per unit charge that passes through a device in the opposite direction to the electric field produced by that device. It is measured in volts.

Sources of electromotive force include electric generators (both alternating current and continuous current types), batteries, and thermocouples (in a heat gradient). [1] Electromotive force is often denoted by or ℰ (script capital E).

Electromotive force is measured in volts (in the International System of Units equal in amount to a joule per coulomb of electric charge). Electromotive force in electrostatic units is the statvolt (in the centimeter gram second system of units equal in amount to an erg per electrostatic unit of charge).

Answer 8

electromotive force(emf) is not a force actually. It is the maximum work done in taking a unit charge once around the whole close circuit

Answer 9

It is the maximum potential difference across the terminals of a source of electricity ,when it is not connected to any external load.