EXPECTED MODEL QUESTIONS +2 HSS 1.Two equal and opposite changes are separated by a small distance (a)What is the name of the above arrangement? Ans. Electric dipole fig. (b)Obtain an expression for electric field intensity on the axial line of the above arrangement? Ans. fig , explanation, derivation ( atleast equation) (c)What is the net force acting on a dipole in a uniform electric field (1) Zero (b)If the above arrangement is placed in a uniform electric field of intensity 3x10-5N/C with its axis perpendicular to the field direction, what is the torque acting on it? Torque = qE x a , where a – length of dipole, q -charge,E- electric field (d) If the arrangement is placed in a uniform electric field, what happens? (1) It will rotate and become parallel to the electric field. Torque = p x E sin 0 = 0.then it will not rotate. 2. In electrostatics, both the electric field intensity (E) and potential (V) are closely related. (a)Write down the relation connecting them p.d = V=E Xd , where d is the distance between the points (b)What do you understand by the term electrostatic potential? V= Work done in moving a +1 C charge from infinity to that point (c)Show that the line integral of electric field along any closed path is zero Ans. derivation 4.A spherical shell of radius R is uniformly charged to a surface charge density S (a)State the theorem which can be used to find the electric field outside the shell. Gauss’s theorm b)Using the theorem arrive at an expression for electric field at a distance r from the centre of the spherical shell (c)It is safe to be inside a vehicle rather than outside, when ever there is lightning and thunder. Comment on this (1) Due to electrostatic shielding. Definition of electrostatic shielding 5.Match the following 1. Coulomb’s law Current 2. Rayleigh’s law Charge 3. Biot Savart Law Electric field 4. Ohm’s law Magnetic field Scattering Refraction 6.Gauss’ theorem is a mathematical relation connecting flux and change (a)What is the relation? (b)State the theorem (c)Using the theorem find the intensity of electric field near an infinite sheet of charge of uniform charge density Ans. fig; , explanation, equation. 7.Capacitors can be connected in series as well as in parallel in a circuit C1>C2>C3, then (a)How will you connect the above 3 capacitors so that their effective value is greater than C1,Justify your answer with the help of a suitable diagram. connecting parallel. fig, explanation. (b)If C1=3mF, C2=2m F and C3=1 m F, what is the effective value in the above combination equation , substitute and calculate. (c)Find the equivalent capacitance b/w two points if all the capacitors have 2mF each and connected series. 8.A glass rod is rubbed with silk (a)What type of charges are developed on then (b)State the two basic properties of electric charge 9.The surface of a charged conductor is an equipotential surface. (a)What is an equi potential surface? If the electric potential at all points are same, then called equi potential surface eg ; surface of a charged sphere (b)What is the work done in moving a charge of 5mc between two points in an equipotential surface Ans . zero ( 0) , becase, work done =p.d = 0 (c)What is the velocity acquired by a particle of mass ‘m’ and charge ‘q’ when accelerated through a potential difference of V volt work done = kinetic energy. qV = ½. mv2 v=... (d) One electron volt of energy is (a)1.6 x 10-13 J (b) 1.6 x 10-19 J (c) 1.6 x 10-9 J (d) 9 x 109J 1eV= 1.6 x 10-19 J 10.An electric current of 2A flows normally through the cross sectional area 10-6m2 of a conductor (a)Is there any relation b/w current and current density? If so what is the relation yes. Current density , j = i/A=nAve /A = nve where, i- current, A- area of cross-section,v-drift velocity. e- charge of electron (b)Calculate the current density in the above case Current density , j = i/A=nAve /A = nve where, i- current, A- area of cross-section,v-drift velocity. e- charge of electron (c)If a metallic wire of resistance 10Ohm is stretched to twice its original length, what happens to its resistance and resistivity? Justify your answer R= 10Ohm , area =A, Length = l, now length = 2l A= A/2. new resistance R = 4R. write the equation & put the values 11.You are given n resistors each of resistance R. (a)How will your combine them to get. (i) maximum and (ii)minimum effective resistance? (b)Find the ratio of maximum to minimum resistance (c)Given the resistance of 1ohm,2ohm, and 3ohm, how will you combine them to get an equivalent resistance 6/11ohm (c)Resistivity of Y is 2.8 x 10-8Wm the number density of electrons in the material is 8.5x1028 per m3.Using the known 566values of mass and change of electrons estimate the value of relaxation time(t). 12.Teacher asks the students to select an experiment from the laboratory which works on Whetstone’s principle? (a)Which experiment they select? meter bridge (b)What is whetstone’s principle? (c)If you are given a resistance wire, resistance box, cell, galvanometer etc in the laboratory, how will you arrange them to find the unknown resistance of the wire. Show it diagrammatically. meter bridge, fig, equation. (d)With the help of above diagram, suggest a method to find. The unknown resistance of the wire fig, equation. explanation 13.You are gives a galvanometer, a low resistance and high resistance. (a)How will you arrange then so that the galvanometer acts as (i) ammeter (ii)Voltmeter a)i) fig , equation, by connecting a small resistance parallel to galvanometer it can be converted to ammeter. ii) fig , equation,by connecting a large resistance series to galvanometer it can be converted to voltmeter. (b)If you are given a potentiometer and a voltmeter, which one will you use to measure potential difference. Justify your answer. Ans. Use potentiometer. Since null deflection method , it doesnot draw any current but voltmeter draws current.So potentiometer gives sharp value. 14 A boy used the following circuit in the laboratory for determining the emf of a cell. i. Identify the principle behind the circuit. Ans. principle of potentiometer. emf of cell in secondary = pd across balancing length E= irl, i-current, r- resistance / length , l- balancing length ii. Modify the above circuit for determining the internal resistance of a cell and hence obtain an expression for the internal resistance of a cell iii. It is considered that this arrangement is better than voltmeter to measure emf of a cell. Do you agree with it? Justify your answer Ans Use potentiometer. Since null deflection method , it doesnot draw any current but voltmeter draws current.So potentiometer gives sharp value. 15.When as electric current is passed through a wire of resistance R, electrical energy is converted into heat energy (a)What is law called ? Ans. Joules law of electrical heating (b)State the law Ans. Q= i2 Rt, where Q-heat energy, i-currentr, R- resistance t - time of flow of current Statement (c)A small heating element made of Nichrome connected to a 100V dc supply draws a current of 20A. How much electric power is supplied to the heater? How much heat is produced in 5 hrs? Q= i2 Rt, power = energy /yime.= i2R 16.A current caring conductor is always associated with a magnetic field. (a)State the theorem which gives the relation b/w current and magnetic field in a closed path Ampers circutal law Exlain with fig & equation (b)Using the above theorem, Obtain an expression for magnetic feild at the midpoint of a long solenoid. (c)What is the value of magnetic field outside the solenoid K.N.HARIHARAPUTHRAN MSc.BEd.SET. 9895739984 If any difficulty call me
Posted on: Sun, 16 Mar 2014 14:50:11 +0000
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