What is different from the EMF voltage

Interestingly, many immediately realized the difference between the EMF and the voltage? And no one correcting the teacher (teacher) in physics, when in practical classes spoke (-la) that we connect is the source of EMF, not voltage? In most cases, we are confused, because the EMF and the voltage is measured in volts. So let's still understand, what is fundamentally different from the EMF voltage.

What is an EMF

So, first let's understand what EMF. Electromotive force (EMF) - is such a physical quantity that characterizes the work of third-party (not potential) power in the AC or the DC source.

In the closed circuit EMF - is the work forces, performed to move a unit charge along the entire outline.

From above presented definition implies the following: EMF sources are forces that are not directly related to the electrostatics, but they are the forces that create the motion of the charge in the closed electric chain.

For example, if mechanical rotation of the rotor winding in the electromagnetic field, it will form the induction electromotive force. The formation of the EMF will be held at each turn separately, but the electromotive force will consist of adjacent windings and at the output we have the sum of all the electromotive force turns.

If you look at the batteries, in which the source of EMF is a chemical reaction.

Additionally sources can act so-called Peltier-elements, in which the EMF generated by thermal heating.

Piezoelectric (when under mechanical action on the material at its ends is formed a potential difference) also relates to EMF sources. However, as the photoelectric effect.

From the examples presented above it is evident that, using various materials and methods for their interaction, EMF can be obtained capable of organizing the ordered motion of charged particles in the closed circuit.

Conditionally accepted that EMF - is the work of 1 joule, performed by moving charge in 1 pendant and is measured in volts.

EMF = 1Dzhoul / 1Kulon = 1 Volt.

Now, let's turn your attention to the tension.

What is the voltage

Thus, the voltage is measured in similar terms, ie in volts. And the tension - a potential difference between two points of the chain. Moreover, these potentials are considered only in an electrostatic field.

So, if we are going to move the charge quantity in 1 pendant and point to point №1 №2, we also we do work in Joel 1, provided that the potential difference between two points is equal to 1 Volt.

Like the same, but in the case of voltage prerequisite it is the presence of an electrostatic field. And where does it come from? So this field source is connected to the circuit source of EMF.

To draw an analogy with the water tower, one can imagine the following picture:

In the picture clearly demonstrated the difference between emf and voltage. The right part of the liquid is moved by the pressure (stress), and the left side by the operation of external forces (emf).

So, if we'll take any electrochemical cell, such as a battery and measure it using a multimeter voltage without a load, so that we obtain the value of the EMF.

If, however, we'll create a closed circuit, which will include any load, then by measuring the voltage the same conclusions batteries, we have already seen the voltage, and it will be somewhat less than the amount EMF.

This is due to the fact that within any source of EMF and internal resistance is present when we connect load voltage drop occurs not only at the ends of the load, but also on the internal resistance EMF source.

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