KVS Class XII PHYSICS 1 KENDRIYA VIDYALAYA SANGATHAN STUDY cum SUPPORT MATERIAL 2014-15 CLASS: XII PHYSICS
KVS Class XII PHYSICS 2 TABLE OF CONTENTS S.No INDEX PAGE No 1 CHAPTERWISE MARK DISTRIBUTION 3 2 STUDY MATERIAL 4 3 FREQUENTLY ASKED QUESTIONS 119 4 SAMPLE QUESTION PAPER 134 5 VALUE BASED QUESTIONS 138 6 GRADE EXERCISE QUESTIONS – LEVEL I,II AND III 156
KVS Class XII PHYSICS 3 CHAPTERWISE MARK DISTRIBUTION 2014-15
KVS Class XII PHYSICS 4 1. ELECTROSTATICS GIST Electrostatics is the study of charges at rest. Charging a body can be done by friction, induction and conduction. Properties of charges: o Like charges repel and unlike charges attract. o Charges are additive in nature i.e., Q= o Charges are quantized. i.e., Q= ± ne [n=1,2,3,… & e=1.602 X10 -19 C] o Charge in a body is independent of its velocity. o Charge is conserved. To measure charge electroscopes are used. Coulomb’s law: k= = 9X10 9 Nm 2 c -2 Where, = permittivity of free space F total = F 12 + F 13 + …. Principle of superposition: [vector sum of individual forces] 1 3 1 2 12 13 2 2 12 13 1 1 .... 4 4 q q q q r r r r Note : In the above triangle the quantity shown at the vertex, could be arrived by multiplying the quantities shown at the base, ie F=E X Q. Any one of the quantity shown at the base is given by the ratio of the quantities shown at vertex & the other quantity shown at the base, ie E=F/Q or Q= F/E Electric field: Force experienced by a unit positive (or test) charge. It is a vector. SI unitNC -1 . 0 o q o F E Lt q Field due to a point charge: Principle of superposition: 1 n total r i E E [vector sum of individual fields] Dipole: Two equal and opposite charges separated by a small distance. Dipole moment: Product of magnitude of charge and distance of separation between them. It is a vector. SI unit: Cm, =Q.2 ; direction of is negative to positive charge. F Q E 1/r 2 E F 1/r 2 Q 1 Q 2 >0 Q 1 Q 2 <0 E r 2
KVS Class XII PHYSICS 5 Dipole in a uniform electric field experiences no net force and instead experiences a torque. = = If = 0 stable equilibrium; If = unstable equilibrium. Electric field due to a dipole o at a point on the axial line : along the direction of dipole moment o at a point on the equatorial line : opposite to the direction of dipole moment. Electric flux: = = ; It is a scalar; SI unit: NC -1 m 2 or Vm. Gauss’ theorem in electrostatics: Uniform Charge distribution : Linear charge distribution: linear charge density Unit Cm -1 ] Surface charge distribution: surface charge density Unit Cm -2 ] Volume charge distribution: Volume charge density Unit Cm -3 ] Applications of Gauss’ theorem for uniform charge distribution: Expression for Infinite Linear Infinite plane sheet Thin spherical shell Flux Magnitude of Field E [for points on/outside the shell] =0 [for points inside the shell] Charge density Properties of electric field lines: Arbitrarily starts from +ve charge and end at – ve charge Continuous, but never form closed loops Never intersect
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- Fall '19