MCQ on Ohms law . Ans. 1.Plot a graph showing variation of current versus voltage for the material GaAs. where R is the constant of proportionality and is known as resistance of the conductor. [Delhi 2009] 6.Define the term mobility of charge carriers in a conductor. How does one explain this behaviour in terms of number density of charge carriers and the relaxation time? I is in the direction of flow of positive charge and opposite to the direction of flow of negative charge. This law cannot be applied to unilateral networks. Compare the drift velocities of electrons in the two wires in both the cases. NOTE Current density is a vector quantity. (a) and (b). 24.A conductor of length / is connected to a DC source of potential V. If the length of the conductor is tripled by gradually stretching it, keeping V constant, how will [Delhi 2014] 22.Draw a plot showing the variation of resistivity of a (i) conductor and (ii) semiconductor, with the increase in temperature. This is done by applying Ohm’s law. The power of the electrolytes to conduct electric current is termed conductance or conductivity. Units: The unit of resistance is ohm In terms of SI, base unit is equal to, (3) Resistivity or specific resistance : We know that resistance R is, Thus, resistivity is defined as the resistance of a conductor of 1 cm length and having area of cross-section equal to. NEET Physics Ohms law Multiple Choice Questions make you feel confident in answering the question in the exam & increases your scores to high. (ii)resistance of the conductor be affected? In mainly dc ammeter and other dc measuring instruments shunt is used to divert current. Therefore, V = RI where R is a constant called resistance. Ans. 2.Show variation of resistivity of copper as a function of temperature in graph. Ans. Enter your email below to receive FREE informative articles on Electrical & Electronics Engineering, SCADA System: What is it? Ans. [Foreign 2014] The constant of proportionality is written as R and this is the resistance value of the resistor. There are thousands of applications of this law in our daily life. When a known voltage is applied across a resistance and the current through the resistance is also known then the value of the reactance can be determined by the relationship: Ohm’s law is a crucial part of a beginners learning of electrical engineering as it is used constantly throughout an electrical engineers career. Ohm’s law first appeared in the book written by Georg Simon Ohm (German) in 1827. 16.Write an expression for the resistivity of a metallic conductor showing its variation over a limited range of temperatures. Answer. [HOTS; Foreign 2012] Ohm’s law deals with the relationship between current, voltage and ideal resistance. It is expressed in Ohm's and is represented as The above equation is known as Ohm's law. 27.The sequence of coloured bands in two carbon resistors Rt and R2 is They are connected Ans. Ans. Ans.Relation between current and drift velocity of electrons in a conductor is given by l = Anevd [Foreign 2008] [Delhi 2014] The relationship between current, voltage and resistance can be written in three different ways. (i)The term drift velocity of charge carriers in a conductor is defined as the average velocity acquired by the free electrons along the length of a metallic conductor under a potential difference applied across the conductor.Its relationship is expressed as [All India 2009c] Ans. Write its SI unit. The basic equation for Ohm’s law is shown below: This relationship was introduced by German physicist George Simon Ohm. 1. More formally, Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points. NOTE Current is a scalar quantity We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites. The cause of conductance is free electrons. It is expressed in Ohm's and is represented as, In SI units, l is expressed in m area of cross-section in, Complete List of Packages for Medical Preparation. When current flows through a resistance there will be a dissipation of power from the resistance. [Delhi 2011] Ans. Use this relation to deduce the expression for the electrical resistivity of the material. Ohm’s Law is a formula used to calculate the relationship between voltage, current and resistance in an electrical circuit. Ans. Ans. Notice: JavaScript is required for this content. When a known current flows through a known resistance the voltage appeared across the resistance can be determined by the relationship [Compartment 2013] Ans.The term drift velocity of charge carriers in a conductor is defined as the average velocity acquired by the free electrons along the length of a metallic conductor under a potential difference applied across the conductor.Its relationship is expressed as (1) Ohm's law: This law states that the current flowing through a conductor is directly proportional to the potential difference across it, i.e., where I is the current strength (In Amperes) and V is the potential difference applied across the conductor (In Volts). 9.Show on a graph, the variation of resistivity with temperature for a typical semiconductor. The number of electrons per second will is (a) 1.6 x 10-19 (b) 3.12 x 10 19 (c) 4 x 10 19 (d) 7.68 x 10 20. If the number density of electrons in X is twice than that in Y, then find the ratio of drift velocity of electrons in the two wires. Ans. We will show only a few of them in this article. 15.The three coloured bands, on a carbon resistor are red, green and yellow, respectively. In voltage divider circuit this law is used to divide source voltage across the output resistance. Ampere is defined as, 2.The current density at a point in a conductor is the ratio of the current at that point in the conductor to the area of cross-section of the conductor at that point provided the area is held normal to the direction of flow of current. Which wire is thicker? (Supervisory Control and Data Acquisition), Programmable Logic Controllers (PLCs): Basics, Types & Applications, Diode: Definition, Symbol, and Types of Diodes, Thermistor: Definition, Uses & How They Work, Half Wave Rectifier Circuit Diagram & Working Principle, Lenz’s Law of Electromagnetic Induction: Definition & Formula. The list will continue as much as you think. [All India 2010] Ans. Register & Get Sample Papers solutions instantly. If the current I ampere flows through a resistance and voltage V volts is the voltage across the resistance then power In SI units, l is expressed in m area of cross-section in so that the units of conductivity are. [All India 2012] Conventional Domestic Fan Regulator is one very common device where the current through the fan gets regulated by controlling the resistance of the regulator circuit. In Case of a Liquid Conductor Like electrolytic solution, there are positive and negative charged ions which can move on applying electric field. 14.Two conducting wires X and Y of same diameter but different materials are joined in series across a battery. 37.Three resistors R1, R2 and R3 are connected in parallel, across a source of emf E and negligible internal resistance. where, n = number of charged particles constitute the current [All India 2011] 33.Define relaxation time of the free electrons drifting in a conductor. How it is related to the drift velocity of free electrons? Ans. Ans. 4.Define the term electrical conductivity of a metallic wire. [Delhi 2014; All India 2014] What is the ratio of the resistances of these two combinations? where (rho) is the constant of proportionality and is called specific resistance or resistivity. Its SI units are Ohm metre But quite often Ohm centimetre is also used. A is cross-sectional area. The main criteria for Ohm’s law is to keep the resistance constant because proportionality constant in the relationship is resistance R. But we know that the variation of temperature affects the value of resistance so to keep the resistance constant during experiments of Ohm’s law the temperature is considered constant. 2. Write its SI unit. [Delhi 2012] (i)drift speed of electrons and Before going to actual topic let us know what is an ideal resistance. 30.Two metallic wires of the same material have the same length but cross-sectional area is in the ratio 1: 2. Copyright © 2010-2019 www.emedicalprep.com. (ii)orange, black, green. Full disclaimer here. [Delhi 2008] From the same relation for a given dissipated power, we can determine the unknown resistance value of either current or voltage is known. If any two of power, current, voltage and resistance are known then with the help of Ohm’s law we can find out other two variables. R depends on the dimensions of the conductor and also on the material of the conductor. [Delhi 2010 C] For a more indepth discussion of Ohm’s law and other fundamental electrical concepts, we would recommend looking at some of the best books for electrical engineers. [All India 2012] Ans.Let potential difference V is applied across a conductor of length / and hence, an electric field E produced inside the conductor. [Delhi 2014] It is represented by the symbol, (Greek kappa). V directly proportional to I V = RI here R is the constant of proportionality called resistence. According to Ohm s law, the electric current through a conductor is directly proportional to the potential difference across it, provided the physical conditions such as temperature and pressure remain unchanged. SI unit of current is ampere and is represented by A. [Delhi 2010 c] cm as the area of cross-section. Ans. with the increase in temperature of a metallic conductor, resistance increases and hence, drift velocity decreases, 8.When electrons drift in a metal from lower to higher potential, does it mean that all the free electrons of the metal are moving in the same direction? e is electron i.e.charge When a known voltage is applied across a resistance and the current through the resistance is also known then the value of the reactance can be determined by the relationship: Ohm’s law is a crucial part of a beginners learning of electrical engineering as it is used constantly throughout an electrical engineers career. 29.Derive an expression for drift velocity of free electrons in a conductor in terms of relaxation time. Write its SI Unit. Answer: (b) 3.12 x 10 19. 17.Define ionic mobility. When a voltage is applied to the electrodes dipped into an electrolytic solution, ions of the electrolyte move and, therefore, electric current flows through the electrolytic solution. curriculum-key-fact Potential difference is a measure of how much energy is transferred between two points in a circuit. 10.Two wires of equal length, one of copper and the other of manganin have the same resistance. where l = current, A = area of conductor, n = number density of electrons and vd = drift velocity. 4.Drift Velocity It is defined as the average velocity with which the free electrons move towards the positive end of a conductor under the influence of an external electric field applied. The limitations of Ohm’s law are outlined below: Electrical4U is dedicated to the teaching and sharing of all things related to electrical and electronics engineering. Use this relation to explain how the resistance of a conductor changes with the rise in temperature ? 3.Flow of Electric Charge in Metallic Conductors Among the solids, all metals are good conductors of electricity. The IUPAC has recommended the use of term conductivity over specific conductance. Ans. NCERT Solutions for Class 6, 7, 8, 9, 10, 11 and 12. e is electron i.e.charge A is cross-sectional area. Ans.Graph of resistivity of copper as a function of temperature is given below (resistivity of metals increases with increase in temperature), 3.Define the term drift velocity of charge carriers in a conductor and write its relationship with the current flowing through it.

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