Emf, or electromotive force, refers to the voltage created by a battery or by a changing magnetic field. Electromotive force is the characteristic of any energy source capable of driving electric charge around a circuit. Electromotive force and circuits an electromotive force emf makes current flow. Photoelectromotive force article about photoelectromotive. Generator or a battery is used for the conversion of energy from one form to another. The driving force which maintains the flow of current in the circuit is called electromotive force it is denoted by e. It can also be defined as the potential difference in charge between two points in a circuit. Electromotive definition, pertaining to, producing, or tending to produce a flow of electricity. Displaying all worksheets related to electromotive force. In this lesson, the physics classroom details that. Counter emf, also called back emf, is a related phenomenon that we will illustrate in. However, emf differs from the voltage output of the device when current flows. The use of newtons second law as a definition of force has been disparaged in some of the more.
Definition of electromotive force in physics, chemistry. Electromotive force is the electric potential generated by either a electrochemical cell or a changing magnetic field. Energy is converted from one form to another in the generator or battery as the device does work on the electric charge being transferred within itself. Describe the electromotive force emf and the internal resistance of a battery explain the basic operation of a battery if you forget to turn off your car lights, they slowly dim as the battery runs down. Find out what you already know about forces, energy. In other words, it is the amount of energy supplied by the source to each coulomb of charge.
The term back electromotive force is also commonly used to refer to the voltage that occurs in electric motors where there is relative motion between the armature and the magnetic field produced by the motors field coils, thus also acting as a generator while running as a motor. The inductance of the loop is going to resist the change in magnetic field within it and an emf will be generated. Electromotive force emf definition of electromotive force. Electromotive force emf is a measurement of the energy that causes current to flow through a circuit.
The emf is the maximum voltage that can be attained by the circuit. Electromotive force meaning in the cambridge english. The reader is reminded of the following definition from section 4. Electromotive force definition is something that moves or tends to move electricity. Electromotive force, energy per unit electric charge that is imparted by an energy source, such as an electric generator or a battery. Electromotive force or emf is a source of energy that can cause a current to flow in an electrical circuit or device. 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. Electromotive force is voltage, or the difference in the electric tension or the difference in charge between two points that causes an electric current. A timevarying magnetic field induces an electromotive force in the plane of the element, driving currents within the conductor. Induced emf definition of induced emf by medical dictionary. The electromotive force emf, of a battery or generator is the potential energy gained by 1 c of charge as it passes from. Sometimes an analogy to water pressure is used to describe. The multitude of alternate expressions for the emf is often. The electromotive force emf of a source of electric potential energy is defined as the amount of electric energy per coulomb of positive charge as the cha rge passes.
The electromotive force is not a force, as force is measured in newtons, but a potential, or energy per unit of charge, measured in volts in electromagnetic induction, emf can be defined around a closed loop as the electromagnetic work that would be transferred to a unit of charge if it travels once around that loop. May 01, 2017 electromotive force can be defined as the energy per unit charge causing the charge to move through the circuit also known as voltage. Electromotive force series electrode reaction standard potential v vs. Analyzing electromotive force and internal resistance. Electromotive force and circuits no steady motion of charge in incomplete circuit. It is abbreviated e in the international metric system but also, popularly, as emf. Emfs convert chemical, mechanical, and other forms of energy into electrical energy. Electromotive force is the energy per unit charge causing the charge to move through the circuit. It is measured in volts and represented by the symbol. Kirchhoffs loop rule is a simplification of faradays law of induction and holds under the assumption that there is no fluctuating magnetic field linking the closed loop.
By the name electromotive force might sound like a force. Electromotive force, or, as it is often written, e. Compare and contrast the voltage and the electromagnetic force of an electric power source. Electromotive force emf, denoted and measured in volts, is the electrical action produced by a nonelectrical source. V, unit of electric potential and electromotive force. Electromotive force definition and meaning collins english. Electromotive force definition in the cambridge english.
Current, resistance and electromotive force electric current. In other words, the car needs batteries to provide an electromotive force emf, which is the energyperunitcharge required to separate electrons in a battery. Electromotive force definition and meaning collins. Electromotive force emf the electromotive force emf is the maximum potential difference between two electrodes of a galvanic or voltaic cell. Simply, it is the work done per unit charge which is the potential difference between the electrodes of the battery measured in volts. Electromotive force is also known as voltage, and it is measured in volts. Emf is the commonly used acronym for electromotive force. It means that, on average, the car increases its speed. Voltage has many sources, a few of which are shown in figure \\pageindex2\. In this study, the concept of friction force, which is frequently encountered in science textbooks, is. Electromotive force article about electromotive force by.
The equation is given by e vlb this equation is true as long as the velocity, field, and length are mutually perpendicular. Electromotive force emf a measure of the strength of a source of electrical energy. Electromotive force and internal resistance physics. Get an answer for explain the factors on which the electromotive force depends. It is defined as the difference of electric potential existing across the ends of a conductor carrying a constant current of 1 ampere when the power dissipated is 1 watt. Electromotive force emf the voltage developed by a battery or a dynamo or any other electrical source of energy is defined as electromotive force or emfs. The electromotive force emf of a source of electric potential energy is defined as the amount of electric energy per coulomb of positive charge as the cha rge passes through the source from low potential to high potential. A device that supplies electrical energy is called electromotive force or emf. Specifically, forces are defined through newtons laws of motion. A force is a push or pull that acts upon an object as a result of that objects interactions with its surroundings. The algebraic sum of the changes in potential encountered in a complete traversal of any loop of a circui t must be zero. Forces resulting from a fall are transmitted up to the spine through the long leg bones and pelvis. Electromotive force, abbreviation e or emf, energy per unit electric charge that is imparted by an energy source, such as an electric generator or a battery. Electromotive force is usually measured in volts volt for alessandro volta, abbr.
Thermoelectromotive force definition is electromotive force in a circuit composed of dissimilar conductors that is produced because of its not being at a uniform temperature throughout. Mar 22, 2017 the definition for electromotive force e. Before tackling the formal definition of force, we examine these intuitive ideas. An emf induced by the motion of the conductor across the magnetic field is a motional electromotive force. These practice questions will help you master the material and.
Electromotive force an overview sciencedirect topics. This quantity is related to the tendency for an element, a compound or an ion to acquire i. The potential difference across the poles of a cell when no current is being taken from it is called the electromotive force emf of the cell i shall use the symbol e for emf question. The electromotive force emf is not really a force but a transfer of electrical energy between high electrical potential and low electrical. Current, resistance and electromotive force 4 definition. Chapter 25 current, resistance and electromotive force. Work done by the source to drive a unit charge round a complete circuit. Emf the energy per unit charge that is converted reversibly from chemical, mechanical, or other forms of energy into electrical energy in a battery or dynamo. Emfthe voltage generated by a battery or by the magnetic force according to faradays law. In the heart it is the power that will take care of the additional circulatory burden imposed by bodily exertion.
A device that converts other forms of energy into electrical energy a transducer, such as a battery converting chemical energy or generator converting mechanical energy, provides an emf as its output. Electromotive force is not considered a force as force is measured in newtons but a potential, or energy per unit of charge, measured in volts. Take a quick interactive quiz on the concepts in what is electromotive force emf. Electromotive force to maintain a steady current in an external circuit we require the use of a source that supplies electrical energy whereas in the external circuit the current flows from higher potential to lower potential, in this source the current must flow from lower potential to higher potential, even though the electrostatic force. In physics, a force is any interaction that, when unopposed, will change the motion of an object. In this device, the charge travels uphill from lower to higher v opposite to normal conductor due to the emf force. Find out information about photoelectromotive force. It is defined as the energy utilized in assembling a charge on the electrode of a battery when the circuit is open.
Electromotive force definition of electromotive force at. The emf is not a force at all, but the term electromotive force is used for historical reasons. Counter electromotive force definition is the electromotive force that develops in some circuits from chemical or magnetic effects of the current and that opposes the impressed electromotive force producing the current called also back electromotive force. What is the meaning of force, mass, and acceleration. Force, in mechanics, any action that tends to maintain or alter the motion of a body or to distort it. Explain the factors on which the electromotive force depends. The electromotive force is the total voltage induce by the source. That is, the same magnetic flux will go through any open surface. Give examples of the devices that can provide the electromotive force. Worksheets are internal resistance, voltage current and resistance, current and resistance, chapter 30 work 1 faradays law of electromagnetic, core practical 3 determine the emf and internal, electromagnetism, work 1 math 285, electric circuits current and resistance chapter 22 and 23.
In an electric circuit there should be a device that acts like the water pump in a fountain source of emf. The term electromotive force is due to alessandro volta 17451827, who invented the battery, or voltaic pile. 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. Electromotive force legal definition of electromotive force. Electromotive force definition of electromotive force by. All such devices create a potential difference and can supply current if connected to a circuit. It is the measure of energy which causes the flow of current through a circuit or conductor denoted in volts or joules per charge. But emf is not exactly a force instead it is the measure of energy or work done per charge which causes the charge to move around in a circuit as shown in the figure below. Electromotive force can be defined as the energy per unit charge causing the charge to move through the circuit also known as voltage.
Electromotive force and thermodynamics electrochemistry. A special type of potential difference is known as electromotive force emf. Electromotive force is directly related to the source of potential difference, such as the particular combination of chemicals in a battery. Electromotive force definition, formula, unit, difference. It is electrical action produced by a nonelectrical source, such as a battery converts chemical energy to electrical energy or generator converts mechanical energy into electrical energy. Electromotive force is defined as the electric potential produced by either electrochemical cell or by changing the magnetic field. Current resistivity resistance electromotive force and circuits energy and power in electric circuits theory of metallic conduction. Chapter 25 current, resistance and electromotive force current resistivity resistance electromotive force and circuits energy and power in electric circuits theory of metallic conduction. Definition of electromotive force in the legal dictionary by free online english dictionary and encyclopedia. It is equal to the potential difference across the terminals of the cell when no current is flowing. Electromotive definition of electromotive by the free. Jul 10, 2019 electromotive force is the electric potential generated by either a electrochemical cell or a changing magnetic field. The potential difference between two points of a conductor creates an electromotive force which pushes free electrons in a conducting material to move towards the positive terminal, creating current.
343 629 21 146 1573 1262 1290 392 224 733 495 1605 750 91 1147 686 560 578 1409 866 948 1508 1033 835 750 1412 264 1241 450 68 1349 195 1311 1274 247 1570 341 1159 1074 100 394 67 1208 1027 727 123 1305 329 1464