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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 Georg Simon Ohm published a book by the name ‘Die galvanischeKette. or amps). when the electric potential difference V is applied across the resistor in unit of volt. In 1872 the unit of electrical resistance was named 'OHM" in his honor. 1.com . mathematischbearbeitet’ meaning "The galvanic circuit investigated mathematically" where he presented the relationship between voltage (V). B and C are partly immersed in electrolyte as shown. 3. Georg Simon Ohm had defined the fundamental interrelationship between current. By observing the results of this experiment. It’s important to note that the resistance R is the property of the conductor and theoretically has no dependence on the voltage applied. This particular equation essentially presents the statement of this law where I is the current through the resistor.Now putting the constant of proportionality we get. measured in Ampere (Ampere. as shown in the figure below. 2.) of the material are changed by any means. The value of R changes only if the conditions (like temperature. current (I). converted by W eb2PDFConvert. Because of this law and his excellence in the field of science and academics. or on the flow of current. and resistance (Ω) based on his experimental data. as shown. and ohm(Ω) is the unit of measure for the resistance of the resistor R. There were two copper electrodes X and Y. A glass container is used to hold the for electrolyte. he got the Copley Medal award in 1841. He performed his experiment with a simple electro-chemical cell. History of Ohm’s Law In the month of May 1827. voltage and resistance of a circuit which was later named Ohm’s law. Reference electrodes A. diameter length etc. is an independent parameter. The atoms and ions are heavier in weight compared to the electrons and therefore have no converted by W eb2PDFConvert.Ohm’s Law Physics To understand the physics behind Ohm’s law in the most simplistic manner possible. we will get less than expected. Thus from here we can reach the conclusion that resistance. 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. which is an inherent property of the conducting material. the more difficulty will be encountered by the current to flow through. let us have a look at this picture below. greater applied force or voltage needs to be applied. As a result. and study it very closely. or the greater the resistance. This is the exact phenomena that occurs even at the molecular level. Or to increase the flow and get a greater required amount of current in the presence of resistance. where a solid conductor contains free electrons which carry negative charge.com . And depending on it are the voltage and current. The more powerful the person at the top is. which are directly and inversely proportional to it respectively. which increases the difficulty for the cause to be fulfilled or in achieving end result. Where as the one at the top is resistance. Let us look into it in detail. This means they acquire some kinetic energy as they move towards the + Ve end of the piece of material (resistor).e. Doubling the voltage would double the rate at which each electron picks up kinetic energy and loses it again by banging into the atoms. current or resistance of a linear circuit when the other two quantities are known to us. Hence the current we get is also proportional to the applied voltage. as it makes them jiggle around and vibrate more furiously due to increased energy level. the rate at which the resistor 'eats up' electrical energy and converts it into heat is proportional to the current also. However. like when we know the value of the resistance for a particular circuit. before they get very far they collide with an atom or ion. So it means twice as many electrons requiring kinetic energy to move them and collie with atoms. This increases the total internal energy of the material and results in heat formation. the power dissipation (rate of energy loss) is P = VI. Again due to presence of static electric field the free electrons again accelerate. The electrons need to be given the required kinetic energy to move them along. in fact it is taken up by the atoms. As a result.contribution towards flow of current. we need not know both the current and the voltage to calculate the power dissipation since P = VI. The average drift velocity of the electrons is proportional to the applied static electric field. In fact they are barriers to the path of the electron flow. This process of drifting or diffusing of electrons in the presence of static atoms and ions. I = V/R to flow through it. This is illustrated in figure below. converted by W eb2PDFConvert. in response to the applied field. Now from law of conservation of energy we know. we apply a voltage V. This equation makes sense since we can expect a higher voltage to make the electrons speed up more swiftly. As a result they tend to "drift" towards the + Ve end. between the leads of a resistor. These barriers are the real cause behind the resistance in a circuit. When. it makes power calculation a lot simpler. The electrons keep being accelerated by the applied static electric field or voltage. we see here that electrical energy is being converted into heat energy and dissipated as loss.com . P. Apart from that. Twice the number of electrons would give us twice the current. in the resistor can be calculated from the equation P = VI. Rather we can use Ohm’s Law. This keeps happening. lose some of their kinetic energy and may bounce back. is the exact reason why materials resist current. This is the physics behind Ohm’s Law. we can expect a current. So. hence they have more energy to lose when they strike an atom. 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. It thus explains why we need to constantly supply the energy to maintain the current. bouncing around from atom to atom on the way. The rate of energy loss or the power dissipation. as it keeps being 'lost' every time they interact with an atom. i. Applications of Ohm’s Law The applications of ohm’s law are that it helps us in determining either voltage. The current we get at any particular voltage depends upon the number of free electrons that are able to flow across. that the energy of electrons lost due to collision is not vanished for ever. the rate at which energy is supplied (or power) gets four times bigger. Non-linear elements are those which do not give current through it. that means the resistance value of those elements changes for different values of voltage and current. A unilateral network has unilateral elements like diode. This phenomena occurs because increasing the voltage also makes the current rise by the same amount as it has been explained above.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. which do not have same voltage current relation for both directions of current. is not exactly proportional to the voltage applied. etc.com . obeying Ohm’s law. Examples of non – linear elements are thyristor. Ohm’s law is also not applicable for non – linear elements. This law cannot be applied to unilateral networks. electric arc. etc. 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.. transistors. When we double the voltage applied to a circuit. that the rate of energy loss varies with the square of the voltage or current. Limitation of Ohm’s Law The limitations of Ohm’s law are explained as follows: 1. 2. converted by W eb2PDFConvert.The content is copyrighted to electrical4u and may not be reproduced on other websites.Silicon Semiconductor Voltage Drop Calculation Insulated Gate Bipolar Transistor | IGBT Thermionic Emission How to Test Capacitors? © 2011-2017 electrical4u.com .