Physics-DPP-3-Electrostatics

PHYSICS Topic: ELECTROSTATICS Date: r r 1. The mathematical form of Gauss’ law is : ε0 òÑE.dS = q In this reference which of the following is correct ? (a) E depends on the charge q which is enclosed within the Gaussian surface only (b) E depends on the charge which is inside and outside the Gaussian surface (c) E does not depend on the magnitude of charge q (d) All of the above ur 2. In a region of space the electric field is given by ˆ ˆ ˆ . The electric flux through a surface of area of 100 units in x - y plane is : E = 8i + 4 j + 3k (a) 800 units (b) 300 units (c) 400 units (d) 1500 units 3. Consider the charge configuration and a spherical Gaussian surface as shown in the figure. When calculating the of the electric field over the spherical surface, the electric field will be due to : (i) q2 (ii) only the positive charges (iii) all the charges (iv) + q1 and – q1 4. A charged ball B hangs from a silk thread S, which makes an angle θ with a large charged conducting sheet P, as shown in the figure. The surface charge density σ of the sheet is proportional to : (a) sin  (b) tan  (c) cos  (d) cot  5. A small charged particle of mass m and charge q is suspended by an insulated thread in front of a very large conducting charged sheet of uniform surface denisty of charge σ . The angle made by the thread with the vertical in equilibrium is : (a) –1 ç σq ö÷ –1 ç σ ö÷ tan ç ÷ (b) tan ç ÷ çè2ε0mg ø÷ (c) –1 æç q ö÷ çèqε0mg ø÷ tan ç ÷ (d) zero çè2σε0mg ø÷ 6. A particle of mass m & charge q is placed at rest in a uniform electric field E as shown & released. The kinetic energy it attains after moving a distance y is : (a) 1 qEy (b) qEy 2 (c) qE 2 y (d) 1 m[qEy] 2 PHYSICS Topic: ELECTROSTATICS Date: 7. A hemispherical surface of radius R is placed with its cross-section perpendicular to uniform electric field E as shown in figure. Flux linked with its curved surface is: (a) zero (b) 2πR2 E E (c) πR2 E (d) 2E0 8. An electric dipole is placed at an angle of 30o with an electric field of intensity 2  105 N/C. It experiences a torque equal to 4 N-m. Calculate the charge on the dipole if the dipole length is 2 cm : (a) 8 mC (b) 4 mC (c) 8 μ C (d) 4 μ C (e) 2 mC 9. A ring of radius R carries a uniformly distributed charge + Q. A point charge – q is placed on the axis of the ring at a distance 2 R from the centre of the ring and released from rest. The particle : (a) executes a SHM along the axis of the ring. (b) moves to the centre of the ring and remains at rest there (c) executes oscillatory motion but not SHM (d) moves through the centre of the ring to infinity along the axis. 10. Two spheres A and B of radius 4 cm and 6 cm are given charges of 80 μC and 40μC respectively. If they are connected by a fine wire, the amount of charge flowing from one to the other is : (a) 20μC from A to B (b) 20 μC from B to A (c) 32μC from B to A (d) 32μC from A to B

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