Physics-DPP-4-Electrostatics

PHYSICS Topic: ELECTROSTATICS Date: 1. A solid conducting sphere of radius a has a net positive charge 2Q. A conducting spherical shell of inner radius b and outer radius c is concentric with the solid sphere and has a net charge – Q. The surface charge density on the inner and outer surfaces of the spherical shell will be : (a) – 2Q 4πb2 , Q 4πc2 (b) (b) – Q 4πb2 , Q 4πc2 (c) (c) 0, Q 4πc2 (d) none of these 2. Three concentric conducting spherical shells carry charges as follows ; + Q on the inner shell, – 2Q on the middle shell and – 5Q on the outer shell. The charge on the inner surface of the outermost shell is : (a) zero (b) + Q (c) – 2Q (d) – 3 Q 3. A thin, metallic spherical sheel contains a charge Q on it. A point charge q is placed at the centre of the shell and another charge q1 is placed outside it as shown in figure. All the three charges are positive. The force on the charge at the centre is : (a) towards left (b) towards right (c) upward (d) zero 4. Two conducting plates A and B each having large surface area S (on one side) are placed parallel to each other. The plate A is given a charge q, while the plate B is neutral. Then the electric field at a point in between the plates is : q q 2q 3 q (a) 2Sε0 (b) Sε0 (c) Sε0 (d) 2 Sε0 5. Three charges Q, + q and + q are placed at the vertices of a right-angled isosceles triangle as shown. The net electrostatic energy of the configuration is zero, if Q is equal to : (a) (b) (c) – 2q (d) + q 6. A point charge q is placed at a distance r from the centre O of an uncharged spherical shell of inner radius R and outer radius 2R. The distance r < R. The electric potential at the centre of the shell will be : (a) q æç1 – çè 1 ö÷ ÷ q (b) (c) q æç1 ç 1 ö÷ ÷ (d) q æç1 ç 1 ö÷ ÷ 4πε0 r 2R ø 4πε0 r 4πε0 èr 2R ø 4πε0 èr R ø PHYSICS Topic: ELECTROSTATICS Date: 7. A solid conducting sphere of radius r is having a charge Q and a point charge q is at a distance d from the center of sphere as shown in the diagram. The electric potential inside the solid sphere is : (a) 1 æçQ – q + çè q ö÷ ÷ (b) 1 æçQ ç Q – q ö÷ ÷ 4πε0 r d ø 4πε0 è r d ø (c) 1 æçQ + çè q ö÷ ÷ (d) none of these 4πε0 r d ø 8. A conducting sphere A is surrounded by two concentric conducting hollow spheres B and C. A is given a positive charge q and C is earthed as shown in the figure. Choose the correct statement : (a) charge density on A,B and C are same q (b) electric field just outside C is 4πε c2 (c) electric field outside C is zero (d) potential inside A is zero 9. A conducting sphere having radius a is charged to a potential V1. Now it is surrounded by another neutral conducting spherical shell of radius b. The potential V2 acquired by the sphere after it is connected to shell by a thin conducting wire is : (a) V a b (b) V b a (c) (c) V1 (a + b) b (d) (d) V1a (a + b) 10. A charge q is distributed over two conectric hollow conducting spheres of radii r and R (> r) such that their surface charge densities are equal. The potential at their common centre is : q (r + R) q é1 1 ù q (r + R) (a) zero (b) 4πε 2 2 2 (c) ê + ú (d) 4πε 2 2 0 (r + R ) 4πε0 êër R úû 0 (r + R ) PHYSICS Topic: ELECTROSTATICS Date: 1. (a) 2. (b) Answer Key 3. (d) 4. (a) 5. (b) 6. (a) 7. (c) 8. (c) 9. (a) 10. (d)

Comments

Post a Comment

Popular posts from this blog

PHYSICS-15-10- 11th (PQRS) SOLUTION

XI (PQRS) PHYSICS REVIEW TEST-5 Select the correct alternative. (Only one is correct) [15 × 3 = 45] There is NEGATIVE marking. 1 mark will be deducted for each wrong answer. Q.31 Two trains, which are moving along different tracks in opposite directions towards each other, are put on the same track due to a mistake. Their drivers, on noticing the mistake, start slowing down the trains when the trains are 300 m apart. Graphs given below show their velocities as function of time as the trains slow down. The separation between the trains when both have stopped, is: (A) 120 m (B) 280 m (C) 60 m (D*) 20 m 1 [Sol: x1 = 2 1 × 10 × 40 = 200 m; x2 = – 2 × 8 × 20 = –80 m  xreletive = x1 + x2 = 280  separation = 300 – 280 = 20 m (D) ] Q.32 One end of a thin uniform rod of length L and mass M is riveted to the centre of a uniform circular disc of radius r and mass 2 M so that the rod is normal to the disc. The centre of mass of the combination from the centre of the disc is at dist
Read more

8-Circular Motion

8.1 (D) The maximum angular speed of the hoop corresponds to the situation when the bead is just about to slide upwards. The free body diagram of the bead is For the bead not to slide upwards. m2 (r sin 45°) cos 45° – mg sin 45° < N (1) where N = mg cos 45° + m2 (r sin 45º) sin 45° (2) From 1 and 2 we get.  = rad / s. 8.2 (C) Let v be the speed of particle at B, just when it is about to loose contact. From application of Newton's second law to the particle normal to the spherical surface. mv2 = mg sin  (1) r Applying conservation of energy as the block moves from A to B.. 1 mv2 = mg (r cos  – r sin ) (2) 2 Solving 1 and 2 we get 3 sin  = 2 cos  8.3 (A) As the mass is at the verge of slipping ∴ mg sin37 –  mg cos37 = m2r 6 – 8 = 4.5   = 3 16 8.4 (B) As when they collide vt  1  72v 2  2 2  25R   R = vt  t =   5R 6v Now angle covered by A =   vt R 11 Put t  angle covered by A = 6 8.5 (C) The acceleration vector s
Read more

4. THEORY-Current Electrictricity

CURRENT ELECTRICITY  1 . ELECTRIC CURRENT (a) Time rate of flow of charge through a cross sectional area is called Current. if q charge flows in time interval t then average current is given by q Iav = t and Instantaneous current i =. lim q  dq t0 t dt (b) Direction of current is along the direction of flow of positive charge or opposite to the direction of flow of negative charge. But the current is a scalar quantity. i i q+ velocity q– velocity SI unit of current is ampere and 1 Ampere = 1 coloumb/sec 1 coloumb/sec = 1A 2 . CONDUCTOR In some materials, the outer electrons of each atom or molecule are only weakly bound to it. These electrons are almost free to move throughout the body of the material and are called free electrons. They are also known as conduction electrons. When such a material is placed in an electric field, the free electrons drift in a direction opposite to the field. Such materials are called conductors. 3 . INSULATOR Another class o
Read more