What is Electromotive Force?

Electromotive Force Definition

Devices that create an EMF (which transforms mechanical energy) include batteries and generators. Batteries turn chemical energy towards electrical energy. Sometimes the analogy of hydraulic pressure is used to describe electromotive force.

In electromagnetic induction, the term “EMF” refers to the electromagnetic energy which would be exerted upon an electric charge (in this instance, an electron) if it went once around the loop.

When a two-terminal device is seen as Thévenin’s equivalent circuit (also known as an electrochemical cell), the equivalent EMF may be computed by the voltage across both of the terminals. The instrument might produce an electric current if an external circuit is attached to its terminals, serving as the circuit’s voltage source.

Overview

EMF is created in nature whenever a surface’s magnetic field changes. As the magnetic field’s lines shift and cross the conductors during a geomagnetic storm, currents flow across an electrical grid whenever the Earth’s magnetic field changes.

You may picture an atomically scaled “charge pump” for each electrode of a voltaic cell. Electromagnetic induction, which refers to the production of electricity by a magnetic field that changes over time inside the generating system, causes a voltage difference between the generator terminals. Charge separation occurs as electrons move from one generator terminal to the next. In the case of an open circuit, an electric field forms but further charge separation is stopped. As a result of charge separation, the electric voltage balances the EMF.

History

In 1801, Alessandro Volta introduced the term “electric motor force” to describe the battery’s active part, which he had created in roughly 1798. The term “electromotive force” is now used in English to describe this.

The “seat of EMF” in a voltaic cell is produced by chemical reactions taking place at every one of both electrode-electrolyte interfaces, Michael Faraday observed in 1830. This indicates that the responses that drive the current lack of an endless supply of energy, as was previously thought. Alessandro Volta formerly had the mistaken belief that the electromagnetic field originated entirely from touch (without taking into account a chemical reaction).

Potential Difference

A potential electrical difference is also known as an EMF. The following examples demonstrate the more formal use when taking into account the distinction between EMF with the potential it generates:

The EMF is solely the product of the battery’s chemistry, which also causes charge separation plus an electrical voltage that drives the current.

Where a transformer linking two circuits is viewed as the source of the electricity for each of the circuits, exactly as if it were produced by an electrical generator, is where the term “transformer emf” originated. The time-varying magnetic field of the electrical generator, which creates a difference in electrical potential that flows to the atmosphere (the applied electrical voltage and a ohmic IR drop are calculated as 0), is the only source of EM radiation in a circuit in an electrical generator driving current through a resistor.

The electrical charge that is separated from itself by the emf-producing mechanism creates an electric field that resists the mechanism for separation when there is an open circuit. For instance, the chemical process in a voltaic cell ends when the opposing electrical fields at each electrode are sufficiently powerful to stop the reactions. A stronger opposing force can reverse activities in so-called reversible cells.

Electromagnetic Induction

Electromagnetic induction is the process through which a time-varying magnetic field produces a rotating electric field. A time-dependent magnetic field can be produced by moving a magnet around a circuit, moving a circuit relative to another circuit (a minimum of one that must be conducting an electric current), or changing the flow of electricity in a stationary circuit.

The electromagnetically induced EMF of a certain circuit is completely controlled by the speed at which the magnetic flux runs through the circuit, following Faraday’s law of induction. In the conductor or coil, an EMF is produced when the flux connections change. Depending upon how they are done, alterations fall into two categories.

When a conductor shifts within a static magnetic field, static induction happens, changing the flux linkage. Motional EMF is another name for the electromotive force that motion creates. According to Faraday’s law of induction, the speed at which the magnetic flux flows through a circuit totally controls the electromagnetically induced EMF of that circuit. When the flux connections change, an EMF is generated in the conductor or coil.