# Emf and voltage relationship

### What is the difference between emf and voltage? | Physics Forums

please elaborate the difference between emf and voltage. This relation is useful because it allows us to predict what the voltage will be at a. The electromotive force (e) or e.m.f. is the energy provided by a cell or battery per In this equation (V) appears which is the terminal potential difference. To find V, the terminal pd (or the voltage available to the external circuit), calculate the Therefore, the 9Ω resistor gets V = IR = x 9 = VSo this 2V emf cell.

## Electromotive force

Volta potential and Electrochemical potential When solids of two different materials are in contact, thermodynamic equilibrium requires that one of the solids assume a higher electrical potential than the other. This is called the contact potential.

The magnitude of this potential difference is often expressed as a difference in Fermi levels in the two solids when they are at charge neutrality, where the Fermi level a name for the chemical potential of an electron system [35] [36] describes the energy necessary to remove an electron from the body to some common point such as ground.

The transfer causes a charge separation, with one body gaining electrons and the other losing electrons. This charge transfer causes a potential difference between the bodies, which partly cancels the potential originating from the contact, and eventually equilibrium is reached.

Internal Resistance of a Battery, EMF, Cell Terminal Voltage, Physics Problems

At thermodynamic equilibrium, the Fermi levels are equal the electron removal energy is identical and there is now a built-in electrostatic potential between the bodies. The original difference in Fermi levels, before contact, is referred to as the emf. No mechanism exists to continue such transfer and, hence, maintain a current, once equilibrium is attained.

One might inquire why the contact potential does not appear in Kirchhoff's law of voltages as one contribution to the sum of potential drops. The customary answer is that any circuit involves not only a particular diode or junction, but also all the contact potentials due to wiring and so forth around the entire circuit.

The sum of all the contact potentials is zero, and so they may be ignored in Kirchhoff's law. Theory of solar cells The equivalent circuit of a solar cell; parasitic resistances are ignored in the discussion of the text.

Solar cell voltage as a function of solar cell current delivered to a load for two light-induced currents IL; currents as a ratio with reverse saturation current I0. Electrically charged bodies can be obtained by separating electrons from the atoms by consuming some other type of energy, e.

## Electromotive Force and Internal Resistance

Such separation exists in electrical sources. Due to the energy activity in the source an EMF is generated, which further induces a surplus of negative charge negative pole and lack of negative charge positive pole.

In electrical engineering the concept of EMF defines the work required to separate the charge carriers in a source of electrical current, in which the force acting on the charges at the ends of the source is not a direct consequence of the field. The unit is same as for voltage V-volt.

The device that supplies the circuit with electric power and produces electromotive force is referred to as the source of electromotive force or shorter EMS electromotive source. There is a difference in the electrical states on the poles terminals of the source.

### Electromotive Force and Internal Resistance

There is a surplus of electrons on the negative pole, and a shortage of electrons on the positive one. In a closed current circuit, electrons move from the negative half to the positive half through the conductors and appliances.

The difference between electric potentials is called electrical voltage [U]. The electrical voltage is equal to the amount of work performed by the electric force in moving the charge from one point of the field to another and that charge.

The electrical voltage is measured in Volt [V].

### Electromotive force - Wikipedia

The voltage measuring instrument is called a voltmeter. Voltage is defined as the difference of electrical potential between two points, and this difference on the poles of the electric source is obtained by removing electrons from one part of the source and transferring them to another.

Expression The electromotive force of the source is equal to the work that some external force has to do to move the charge unit from one pole of the source to another, but through the source. Voltage in the outer part of the circuitry is much equal to the work that needs be done by the electric force to move the charge unit from one pole of the source to the other, but through the wire.