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BAL BHARATI PUBLIC SCHOOL, PITAMPURA WORKSHEET – 1 Electrostatics(1) Name :______________________________ Date:____________ 1. A charge q is placed at the centre of the line joining 2 equal opposite charges Q, The system of the three charges will be in equilibrium if q is equal to (a) – Q/2 (b) – Q/4 (c) Q/4 (d) Q /2 2. Two spherical conductors B and C having equal radii and carrying equal charges in them repel each other with a force F when kept apart at some distance .A third spherical conductor having same radius but uncharged is brought in contact with B then brought in contact with C and finally removed away from both. The new force of repulsion between B and C is (a) F/4 (b) 3F/4 (c) F/8 (d) 3F /8 3. A charged oil drop is suspended in uniform field of 3X10 4 V/m so that it neither rises and falls. The charge on the drop is (mass of drop is 9.9 X10 -15 kg and g is 10m/s 2 ) a. 3.3 × 10 -18 C b. 3.2 × 10 -18 C c. 1.6×10 -18 C d. 4.8 × 10 -18 C 4. Two point charges +8q and -2 q are located at x=0 and x=L respectively .The location of a point on x axis at which the net electric field is zero is a. 2L b. L/4 c. 8L d. 4L 5. An electric dipole is placed at an angle of 30° to a uniform electric field .The dipole will experience a. a torque and translational force b. a torque only c. a translational force only in the direction of the field d. a translational force only in the direction normal to that of field 6. Explain why two field lines never cross each other at any point? ................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... 7. Three small charges of equal magnitudes and same sign lie on the circumference of a circle forming an equilateral triangle .What is the value of electric field intensity at the centre of circle? 8. Four point charges q A = 2 C, q B = – 5 C, q C = 2C, and q D = – 5 C are located at the corners of a square ABCD of side 10 cm. What is the force on a charge of 1 C placed at the centre of the square? 9. A point charge causes an electric flux of – 1.0 × 10 3 Nm 2 /C to pass through a spherical Gaussian surface of 10.0 cm radius centred on the charge. (a) If the radius of the Gaussian surface were doubled, how much flux would pass through the surface? (b) What is the value of the point charge? 10 Electric field in the above figure is directed along + X direction and given by Ex = 5Ax + 2B, where E is in NC-1 and x is in metre, A and B are constants with dimensions Taking A= 10N/m/C and B = 5NC-1 calculate. (i) the electric flux through the cube. (ii) net charge enclosed within the cube. _______________ __________________ Teacher’s signature Grades/Score BAL BHARATI PUBLIC SCHOOL, PITAMPURA WORKSHEET – 2 Electrostatics(2) Name :______________________________ Date:____________ 1. A positive charge of size q is held in an electric field at point Y as shown in the diagram. It is moved, without acceleration to point X and held there. a. What was the force needed to hold the charge at Y?____________ b. What is the force needed to move the charge from Y to X?_______ c. Is work done in moving the charge from Y to X?________________ d. Does the charge have potential energy at both X and Y?__________ e. By how much does the amount of potential energy at X differ from that at Y?__________ f. Is this amount in (e) a gain or a loss in potential energy at X?__________________ g. Although the electric field is the same at X and Y, how do we describe the situation where the charge has more potential energy at X then at Y? ______________________ 2. Three points are shown in a uniform electric field. (a) At what point is the potential the highest? ________________ (b) How does the potential at B compare to that at C? ____________ (c) What name is given to the dotted line through B and C?__________ (d) How does the amount of work done in moving a charge from C to A compare to moving the same charge from B to A? __________________________ 3. (a)What is the potential difference between two points X and Y in an electric field if an amount of work equal to 5.5 J has to be done on a charge of +0.5C to move it from X to Y? (b) Does the charge in (a) have to be moved in a direct line from X to Y?___________ (c) Which point X or Y is at the higher potential?_______________________ 4. Two charges q 1 and q 2 are of values – 5.0 10 -8 C and +3.0 10 -8 C, respectively. They are separated by a distance of 20.0 cm. Find the electric potential at a point midway between them, due to: (i) q 1 (ii) q 2 (iii) both q 1 and q 2 . 5. Point charges of 3 x 10 -9 C are located at two vertices of an equilateral triangle of side 20 cm. How much work will be done to bring a test charge of 10 -19 C from infinity up to the third corner of the triangle? 6. Three capacitors of capacitances 2pF, 3pF and 4pF are connected in parallel.(a) What is the total capacitance of the combination? (b) Determine the charge on each if the combination is connected to a 100 V supply. 7. If C 1 = 20 F, C 2 = 30 F and C 3 = 15 F, one of the plate of C 1 is connected to a potential of 90V, one plate of C 3 is earthed. What is the potential difference between the plates of C 2 . 8. A parallel plate capacitor is charged by a battery which is kept connected to the battery. The space between the plates is then filled with a dielectric. How are the values of (i) charge on the plates (ii) capacitance (iii) potential difference between the plates (iv) electric field between the plates and (v) energy stored in the capacitor affected due to the introduction of the dielectric? 9. Can electric potential be zero at a point where electric field is not zero? _______________ __________________ Teacher’s signature Grades/Score 90V C 3 C 2 C 1
