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MENUOhms Law | Equation Formula and Limitation of Ohms Law Like 16 2 Next » The most basic quantities of electricity are voltage, current and resistance. Ohm's law shows a simple relationship between these three quantities, hence this law can be considered as the most basic law of electrical engineering. This simple, easiest to remember, three character law of electrical engineering helps to calculate and analyze electrical quantities related to power, efficiency and impedance.Ohm's law first appeared in the book written by Georg Simon Ohm (German) in 1827. Statement of Ohm’s Law The statement of Ohm’s law is simple, and it says that whenever a potential difference or voltage is applied across a resistor of a closed circuit, current starts flowing through it. This current is directly proportional to the voltage applied if temperature and all other factors remain constant. Thus we can mathematically express it as: converted by W eb2PDFConvert.com diameter length etc. Georg Simon Ohm published a book by the name ‘Die galvanischeKette. or amps).Now putting the constant of proportionality we get. he got the Copley Medal award in 1841. This particular equation essentially presents the statement of this law where I is the current through the resistor. Georg Simon Ohm had defined the fundamental interrelationship between current. current (I). History of Ohm’s Law In the month of May 1827. converted by W eb2PDFConvert. He performed his experiment with a simple electro-chemical cell. The value of R changes only if the conditions (like temperature. There were two copper electrodes X and Y. when the electric potential difference V is applied across the resistor in unit of volt. as shown in the figure below.) of the material are changed by any means. B and C are partly immersed in electrolyte as shown. and resistance (Ω) based on his experimental data.com . Reference electrodes A. mathematischbearbeitet’ meaning "The galvanic circuit investigated mathematically" where he presented the relationship between voltage (V). 1. measured in Ampere (Ampere. 3. or on the flow of current. Because of this law and his excellence in the field of science and academics. By observing the results of this experiment. voltage and resistance of a circuit which was later named Ohm’s law. A glass container is used to hold the for electrolyte. It’s important to note that the resistance R is the property of the conductor and theoretically has no dependence on the voltage applied. as shown. 2. In 1872 the unit of electrical resistance was named 'OHM" in his honor. and ohm(Ω) is the unit of measure for the resistance of the resistor R. Or to increase the flow and get a greater required amount of current in the presence of resistance. The atoms and ions are heavier in weight compared to the electrons and therefore have no converted by W eb2PDFConvert. and study it very closely. This is the exact phenomena that occurs even at the molecular level. we will get less than expected. Where as the one at the top is resistance. let us have a look at this picture below.com .Ohm’s Law Physics To understand the physics behind Ohm’s law in the most simplistic manner possible. which increases the difficulty for the cause to be fulfilled or in achieving end result. the more difficulty will be encountered by the current to flow through. which is an inherent property of the conducting material. Thus from here we can reach the conclusion that resistance. As a result. From here we can draw the analogy that the person at the extreme left is the cause or the external force due to which current (or the person in the middle) tends to flows across a particular circuit from one end to the other in the direction of the applied voltage. greater applied force or voltage needs to be applied. is an independent parameter. which are directly and inversely proportional to it respectively. or the greater the resistance. where a solid conductor contains free electrons which carry negative charge. The more powerful the person at the top is. And depending on it are the voltage and current. the rate at which the resistor 'eats up' electrical energy and converts it into heat is proportional to the current also. These barriers are the real cause behind the resistance in a circuit. The electrons keep being accelerated by the applied static electric field or voltage. This process of drifting or diffusing of electrons in the presence of static atoms and ions. So it means twice as many electrons requiring kinetic energy to move them and collie with atoms. However. As a result they tend to "drift" towards the + Ve end. So. This increases the total internal energy of the material and results in heat formation. in fact it is taken up by the atoms. This equation makes sense since we can expect a higher voltage to make the electrons speed up more swiftly. Let us look into it in detail. Doubling the voltage would double the rate at which each electron picks up kinetic energy and loses it again by banging into the atoms. we see here that electrical energy is being converted into heat energy and dissipated as loss. It thus explains why we need to constantly supply the energy to maintain the current. in the resistor can be calculated from the equation P = VI. As a result. Apart from that. The average drift velocity of the electrons is proportional to the applied static electric field. I = V/R to flow through it. converted by W eb2PDFConvert. i. current or resistance of a linear circuit when the other two quantities are known to us.contribution towards flow of current. Again due to presence of static electric field the free electrons again accelerate. In fact they are barriers to the path of the electron flow. The current we get at any particular voltage depends upon the number of free electrons that are able to flow across. hence they have more energy to lose when they strike an atom. When. is the exact reason why materials resist current.e. before they get very far they collide with an atom or ion. This is illustrated in figure below. The rate of energy loss or the power dissipation. as it keeps being 'lost' every time they interact with an atom. This is the physics behind Ohm’s Law.com . bouncing around from atom to atom on the way. it makes power calculation a lot simpler. Hence the current we get is also proportional to the applied voltage. we need not know both the current and the voltage to calculate the power dissipation since P = VI. Applications of Ohm’s Law The applications of ohm’s law are that it helps us in determining either voltage. between the leads of a resistor. Rather we can use Ohm’s Law. the power dissipation (rate of energy loss) is P = VI. P. This means they acquire some kinetic energy as they move towards the + Ve end of the piece of material (resistor). Now from law of conservation of energy we know. Twice the number of electrons would give us twice the current. This keeps happening. lose some of their kinetic energy and may bounce back. like when we know the value of the resistance for a particular circuit. we can expect a current. The electrons need to be given the required kinetic energy to move them along. in response to the applied field. as it makes them jiggle around and vibrate more furiously due to increased energy level. The way the electrons move through the solid material is a bit like the way toothpaste squeezes along a tube or as shown in the comic picture above. we apply a voltage V. that the energy of electrons lost due to collision is not vanished for ever. that the rate of energy loss varies with the square of the voltage or current. A unilateral network has unilateral elements like diode.To replace either the voltage or current in the above expression to produce the result These are the applications of Ohm’s law as we can see from the results. is not exactly proportional to the voltage applied. This law cannot be applied to unilateral networks. that means the resistance value of those elements changes for different values of voltage and current. etc.. electric arc. Non-linear elements are those which do not give current through it. 2. This phenomena occurs because increasing the voltage also makes the current rise by the same amount as it has been explained above. Ohm’s law is also not applicable for non – linear elements. Limitation of Ohm’s Law The limitations of Ohm’s law are explained as follows: 1.com . obeying Ohm’s law. transistors. the rate at which energy is supplied (or power) gets four times bigger. When we double the voltage applied to a circuit. which do not have same voltage current relation for both directions of current. etc. Examples of non – linear elements are thyristor. Like 16 2 Next » Closely Related Articles Joules Law of Heating Faraday Law of Electromagnetic Induction Lenz Law of Electromagnetic Induction Faraday First and Second Laws of Electrolysis Coulombs Law | Explanation Statement Formulas Principle Limitation of Coulomb’s Law Biot Savart Law Gauss Theorem Fleming Left Hand rule and Fleming Right Hand rule Seebeck Effect and Seebeck Coefficient Wiedemann Franz Law More Related Articles New Articles Step Up Transformer converted by W eb2PDFConvert. 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