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@mostwantedneetofficial, , Electric Charges and Fields Chapter, , , , (@) ELECTRIC CHARGE (3) CONDUCTORS AND INSULATORS (@ CHARGES INTERACTION, , Positive and negative charges were named by Benjamin Franklin. | Some substances which readily allow passage of | | Coulomb's law is quantitative statement about force, , Charging can be done by electricity through them are called conductors between two point charges., , 1. Friction 2. Induction 3. Conduetion » Metals, human body and earth are conduc > Force varies inversely as square of distance between, Charging by friction » Materials which opposes flow of charge through ther the charges and directly proportional to product of, When glass rod is rubbed with silk, the rod acquires one type are insulators., , of charge and silk acquires other type of charge. Glass, porcelain, pias!, HE, , PROPERTIES OF CHARGES Aprocess.of sharing chatges with, , magnitude to two charges and acts along the line, , joining two charges, , Two charges q, and q, separated by distance rin, , vacuum, the magnitude of force (F) between them, Two types of charges exist orearthifig faa, , > Like charges repel unlike attract. aK, , Abody is charged by loss or gain of electrons x depends on system of units and medium. In SI unit, » Inanisolated systems, total charge remains conserved aM cicctrolope de n yatulum K= 9 * 10°, Unit of charge is coulomb(C), » Charge exists in discrete nature. q=+nxe Charge 18 Salar and additive in nature. | 1 (9) = 8.854 « 10° CN, , Moving charge has magnetic effects along with 7, , , , @ FORCE BETWEEN MULTIPLE CHARGES 6) ELECTRIC FIELD OF GHARGES, = | aint producés an elec id everyy jing. V rt Sr, REGED an charje tiie io raenber or olher chaies ix of all | | 2sAteharge placed ata point protiucés an electric field everywhere in the surrounding. When another charge is, |,J/ ‘Drought in els, neve ther® acts on it and produces a force. Faraday introduced field concept, the forces on that charge due to the other charges, taken one at a.ifieyithe, »/ Electri¢liels intensity produéed by a charge Qata point distance ris given by, individual forces are unaffected by presence of other i, , Et =, as superposition principle of electrostatics, Vector sum of forces is obtained | ‘, , by parallelogram law of addition of vectors. Force on first charge due ta othier Si unit of aietiric field is N/C. Field intensity at a point due to charge Q in space is defined as the force, , that’s unit positive charge would experience if placed at that point, isgivenas F,, , tim {F_), > Exqno\ a), , @ ELECTRIC DIPOLE, An electric dipole is an arrangement of pair of equal and opposite point charges separated by, a distance., , | > Field vary from point to point and is a vector quantity. Field can transport energy., > Direction from -q to +q is direction of dipole moment. Field Due to System of Charges, , |, , |, , |, , ‘3 Electric fields due to dipole 1 Electric field at a point P in space due to system of charges is defined as force, , , , experienced by a unit test charge placed at that point, On Axis of Dipole On Equatorial Plane, , 2rd 22 (itr>>a) aan (ifr>>a), , Er), , , , ay, , , , , , , , , , Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456

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@mostwantedneetofficial, , Electric Charges and Fields, , NCERT Maps, , , , » Polar molecule : HO have permanent electric dipole moment even in absence of electric field 0) ELECTRIC FLUX, , » Non polar molecule : CH,, CO,. The Dipole moment is zero., » Adipole in external uniform electric field experience torque but no net force, , : QE —>eE, pre ae oo t e 1] = PE sind PY a =, QE <— —, Force Force, , Similar to fluid flow an analogous quantity exists in electrostatic called electric flux, There is no flow of observable quantity., , » The number of (field) lines crossing a unit area placed normal to field at @ point is, measure of strength of electric field at that point., , of field lines crossing AS area is proportional to EAScos0. This is called, , , , , , (® ELECTRIC FIELD LINES, , (Lines of force by Faraday), Field lines carry information about direction of X / wok fet, , electric field at different points in space. Relative, , density of field lines at different points indicates en, relative strength of electric fields at these points. h, Faraday introduced non mathematical way of, , visualizing electric field around charge, , configuration., , 9) ELECTRIC FIELD LINES PROPERTIES, Itis a way of pictorially mapping the electric field around a configufation 6f charges., Aline is a curve drawn in such a way that tangent to it at each pointisin the ditection of, net field at that point., Afield line is a space curve (Acurve in three dimension), Field lines of a single positive charge are radially outward, Field lines start from positive charges and end at negative charges, From a single charge, line can start from or end at infinity., Ina charge free region, electric field lines can be taken to be continuous curves, without any breaks., Two field lines can never cross each other., Electrostatic field lines don’t form any closed loop. This follows from their, , conservative nature, , , , Region of, , flux through area element AS, , 4 outward drawn normal to area element AS, , Total flux pate AS, Approximate sign is becau:, WAS >0then, =) Eds, , ectric field is taken uniform over area element., , @)Gauss's LAW, , Total electric flix through closed Surface s = — , where q = Total charge enclosed by, , Toial flux is zer0 if closed\strface encloses no charge., , ‘Gauss Ja is trué'for ny surface. no matter what its shape or size is, , @'S total. charge enclosed by surface, located anywhere inside., , Gaussian surface should not pass through discrete charges, , Any violation of Gauss's law will indicate departure of inverse square law, Application of Gauss's law, , Electric field due to infinitely long wire, , E= at distance r from linearly charged rod., Ones, Field of Uniformly Charged Shell » Electric field due to infinite plane sheet, a ., , A is independent of distance from sheet., , Directed out for q > 0, directed inwards for q < 0, E=0 (r<R) field is zero inside shell, , , , , , Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456

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@mostwantedneetofficial, , NCERT Maps, , Electric Charges and Fields, , , , 2, , 3., , 4, , Sharpen Your Understanding, , The electrostatic force between two small, , charged spheres having charges of 2 = 10, C and 3 x 10°C placed 30 cm apart in air is, [NCERT Pg. 46], , (2) 0.6N, , (4) 1.8N, , (1) 0.9N, (3) 1.2N, Four point charges q, =-2 uC, gg =-5 uC,, Ac =-2 uC and gp =-5 uC are located at, , the corners of a square of side 20 cm (In, cyclic order). What is electric force on a, charge of 1 uC placed at the centre of, square? [NCERT Pg. 46], , (1) 0.9N (2) Zero, (3) 0.6 N (4) 2.4N, , A system of two charges q, =2.5x10°C, , and 9g =-2.5x10"' Care located at points, , A: (0, 0, — 15 cm) and B: (0, 0, 15 cm), respectively. The electric dipole moment of, system is [NCERT Pg. 46), , (1)2.5*107Cm (2) 5*107Cm, (3) 7.5* 10%Cm (4) Zero, , A polythene piece rubbed with wool is found, to have negative charge of 3.2 x 10° C. The, number of excess electrons on polythene is, , NCERT Pg. 46], (2) 4 10, (4) 6 = 1070, , (1) 2* 10%, (3) 5.5 « 10°, , , , An electron falls through distance of, 2 * 10 m in uniform electric field from state, of rest. The time of fall if E = 6 x 10* NC~Tis, , [NCERT Pg. 21], , (1) 1.5* 10%s, , (2) 1.94 x 10-9 s, , (3) 3.3 * 105s, , (4) 2.3 10s, , Considérecharges \g, —q and q placed at, vertices of an equilateral triangle as shown, , in figure. Calculate force on -q charge due, to other. [NQERT Pg, 17], , q, , (1, Ore, , (3), , Teg, Which among the given statements is, incorrect statement? (NCERT Pg. 19), , (1) For every positive point charge, electric, field lines will be directed radially, outwards from charge., , (2) Magnitude of electric field E will depend, on distance form point charge, , , , NCERT Based MCQs, , (3) The electric field due to a point charge, has spherical symmetry, , (4) A test charge q experiences electric, force F at a point then electric field, , : F, intensity is defined as E = —, q, , A proton and an electron are released form, rest in uniform electric field then the correct, statement among the following is, , [NCERT Pg. 46], , (1) Time required to fall through certain, distance is more for an electron, , (2). The force experiences by proton will be, more, , (3) Magnitude of acceleration experienced, by proton is more, , (4) KE gained by both charges in moving, through same distance are equal, , Regarding electric lines of force, the correct, statement is/are INCERT Pg.24], , (1) Field lines carry information about, direction of electric field, , (2) Relative density of field lines at different, points indicates relative strength of, electric field at these points, , (3) The field lines crowd where field is weak, and spaced apart where field in strong, , (4) Both (1) and (2) are correct, , , , Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456

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Ea Electric Charges and Fields, , @mostwantedneetofficial, , NCERT Maps, , , , 10, , The incorrect statement among the following, , statements is [NCERT Pg. 25], , (1) Electric field lines can never cross each, other, , (2) Electrostatic field lines do not form any, closed loop, , (3) In charge free region, electric field lines, can be taken to be continuous curve, , (4) Field lines around a system of two, positive charges is straight and parallel, lines pictorially, , A dipole consist of two charges q and -q, , separated by a distance 2a. The electric field, , of this dipole at distance r from centre of, , dipole at a point A on axis is [NCERT Pg.28), , 2p, () a (2) —*P___, , 4neq(r? +a")?, , 2pr, , 4) ——>—, 4ne,(r? -a°)P, , Electric field, 1, , E, =100x?, E, =E, =0, , components are, , Calculate net, , electric flux though the cube placed in, electric field at shown position., , INCERT Pg. 35], it, , 1 3m, , 6 y, , —, 1m, , , , , , , , x axis, , , , , , 3m, , , , z <3m>, , (2) 1800 Nm?2C-*, (4) 3600 Nm2c-*, , (1) 900 Nm?C~*, (3) 600 Nm?C~*, An infinite long straight wire has linear, charge density 2 = 4 x 10° C m. The, electric force experienced by a proton at, , perpendicular distance of 10 mm from axis, of wire is (NCERT Pg. 37], , (1) 1.25 x 10*N, (3) 2.8 x 10°°N, , (2) 1.68 x 10° N, (4) 1.15 * 10°°N, , Coulomb's law of electrostatic for the force, between two point charges most closely, resembles NCERT Pg M2], , (1) Law of conservation of charges:, (2) Law.of conservation of energy, , (3) Newton's second law of motion, (4) Newton's law of gravitation, , A point charge ¢ of mass mis placed in front, ofa uniformly charged infinite sheet and, released. The surface charge density of, sheet isc C m=?) The kinetic energy of, charge after t second is [NCERT Pg. 39], , q’o2t?, eam, , 2 eye, moet (2), 4e5m, , q?o*t? q?o2t?, , 3) (4, , 8<3m ) 4egm?, , An electric dipole consists of two equal and, opposite charges 0.02 C separated by, 2 mm. The dipole is placed is uniform, , , , electric field of 107 N C~'. Maximum torque, exerted by field on dipole is, , [NCERT Pg. 31], (2) 4* 104 Nm, (4) 2* 10% Nm, , (1) 2* 104Nm, (3) 8 104 Nm, , A thin spherical shell is given a charge, q = 4 uC, uniformly distributed over its, surface. Consider a point P outside the shell, at distance of 2 m from surface. If the radius, of shell is 1 m, what is electric field at point, P? [NCERT Pg. 39}, , (1) 4kN C+ (2) 2kNC", (3) 9 kN C+ (4) 36 kN C+, Figure shows track of three positive charged, particles through uniform electric field E. All, charges are equal in value. Which charge, , particle has more initial kinetic energy on, entering horizontally between the plate?, , [NCERT Pg. 47], , Plate, Fees eeeres, , Plate, , (1) Particle 1, , (2) Particle 2, (3) Particle 3, (4) Both 1 and 2 have equal initial KE, , , , Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456

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@mostwantedneetofficial, , NCERT Maps, , Electric Charges and Fields Ee, , , , 19. A uniformly charged conducting sphere of, , 3 m diameter has a surface charge density, of 90 yC/m?. What is total electric flux, leaving the surface of sphere?, , [NCERT Pg.48], (1) 1.76 x 108 N m2C-1, (2) 2.87 x 108 N m2C-1, (3) 5.2 « 108 N m2C~t, (4) 4.52 * 10°N m?@C, , When a charge is put on an insulator, it, stays at same place, when some charge is, transferred to conductor it gets distributed, over surface of conductor., , INCERT, A body is positively charged by, electrons and negatively charged by, electrons. [NCERT Pc, A simple apparatus to detect charge on a, bodyis INCERT Pg. 3], When electrified rods are brought near light, objects. The rod induces opposite charges, on near surface of the objects and similar, type of charges move to farther side of, objects, this method is called _, , [NCERT Pg. 6], Experimentally, it is established that all free, charges are integral multiple of basic unit of, charge. This discrete nature of charge is, called of change. [NCERT Pg. 08}, , , , 20, , Incorrect statement among the following is, [NCERT Pg.48], , (1) Gauss’s law is useful in calculating, electric field when system has some, symmetry, , (2) Gaussian surface can pass through a, , continuous charge distribution, , @Ihinking in Context, , SI units of absolute permittivity of free space, is_\ NCERT Pg. 11], Coulomb's law.of electrostatic agrees with, the Newton's law. [NCERT Pe. 42, The ratio of electrostatic force between two, protons to_ gravitational force at “same, separation in vacuum is __, , (NCERT Pg. 13], Experimentally it is verified that force on any, charge due to number of other charges is, the vector sum, of all the forces on that, charge due to other charges. This is termed, as . [NCERT Pg. 15], Away from a point charge, the field gets, weaker and density of field lines is less,, resulting in well separated field line away, from charge. This statement is, , [NCERT Pg. 23], , (1) True (2) False, , , , (3) Gauss’s law is based on inverse square, , dependence of electric field on distance, , (4) In situation when surface is so chosen, that some charges are outside and some, inside, electric field (whose flux appears, on left side of Gauss’s equation) is only, due to the charges inside the closed, surface, , Electrostatic field lines do not form any, closed loops. This follows from the, conservative nature of electric field. The, statement is [NCERT Pg. 25), (1) True (2) False, Total charge of electric dipole is . The, electric field at distance much larger than, dipole length of a dipole, on a plane, perpendicular to dipole axis varies as___., NCERT Pg. 27], Total electric flux through a closed surface, , is equal to 7, here qis, £9, [NCERT Pg. 34], Ina situation when surface is so chosen that, there are some charges inside and some, outside. The electric field whose flux, appears on left side of Gauss's equation is, due to all charges the surface., [NCERT Pg. 34], , , , Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456