Anyone who chose the repair and maintenance of electrical installations of its specialty, is well known to the approval of teachers: "Ohm's law for closed circuit you need to know.Even waking up in the night, it is important to be able to formulate it.Because it is the basis of all electronics. "Indeed, the regularity discovered an outstanding German physicist Georg Simon Ohm, influenced the subsequent development of the science of electricity.
In 1826, conducting experiments on the passage of an electric current through a wire, ohms revealed a direct correlation between the strength of the current supplied to the circuit power supply voltage (although in this case it is more correct to speak of the electromotive force EMF) and the resistance of the conductor.Dependence has been theorized as a result appeared Ohm's law for closed circuit.An important feature: the relevance of the identified fundamental law is valid only in the absence of external disturbing force.In other words, if, for example, the conductor is in an alternating magnetic field, direct application of the formulation is not possible.
Ohm's law for closed circuit has been identified in the study of the simplest circuits: power supply (having EMF) from its two terminals to the resistor are conductors, in which there is the directional movement of bearing a charge of elementary particles.Hence, the current is the ratio of electromotive force to the total resistance of a circuit:
I = E / R,
where E - electromotive force of the power supply, measured in volts;I - a value of current in amperes;R - the electrical resistance of the resistor in ohms.Note that Ohm's law for closed circuit takes into account all the components of R. In a complete closed-loop calculations for the amount of R understands the resistor, conductor (r), the power supply (r0).That is:
I = E / (R + r + r0).
If the source impedance r0 is greater than the sum of R + r, the current does not depend on the characteristics of the connected load.In other words, the source voltage in this case is a current source.If the value of r0 is less than R + r, then the current is inversely proportional to the total external resistance, and the power supply generates a voltage.
When performing accurate calculations take into account even the voltage loss in the joints.Electromotive force is determined by measuring the potential difference across the terminals of the source when the load is off (open circuit).
Ohm's law for subcircuit are used just as often as for closed loop.The difference is that the calculations do not include the EMF, and a potential difference.This section is called homogeneous.In this case, there is a special case, which allows to calculate the characteristics of the circuit in each of its elements.We write it in the form of the formula:
I = U / R;
where U - voltage, or potential difference in volts.It is measured by a voltmeter connected in parallel probes to the terminals of an element (resistance).The resulting U-value is always less than the EMF.
Actually, that this formula is the most famous.Knowing any two components of the formula, you can find a third.Calculation of circuits and components is carried out by the law in question for the current loop.
Ohm's law for the magnetic circuit is in many ways similar to its interpretation of the electrical circuit.Instead of a closed magnetic circuit conductor used, the source is a coil winding current passing through the turns.Accordingly, there is a magnetic flux of magnetic circuit closed.The magnetic flux (F) circulating along the contour directly depends on the MDS (magnetomotive force) and the resistance of the material passing the magnetic flux:
F = F / Rm;
where F - flux in Weber;F - MDS in amperes (sometimes Gilbert);Rm - resistance, causing attenuation.
