H213 Electric Fields - 2. Tutorial wSolutions (1718) (Updated 28 Feb)

9749 H2 Physics Tutorial w/ Solutions Topic 13: Electric Fields Page 1 of 22 Topic 13 Electric Fields Data Formulae electric potential, V = 4 o Q r Multiple Choice Questions 1 The diagram shows a non -uniform electric field near a positively charged and a negatively charged sphere. Four electrons, A, B, C and D, are shown at different positions in the field. On which electron is the direction of the force on the electron shown correctly? permittivity of free space, εo = 8.85  10–12 F m–1 (1/(36 π))  10–9 F m–1 elementary charge, e = 1.60  10–19 C unified atomic mass constant u = 1.66  10–27 kg rest mass of electron, me = 9.11  10–31 kg rest mass of proton, mP = 1.67  10–27 kg

9749 H2 Physics Tutorial w/ Solutions Topic 13: Electric Fields Page 2 of 22 2 The diagram shows the electric field near a point charge and two electrons X and Y. Which row describes the forces acting on X and Y? direction of force magnitude of force on X A radially inwards less than force on Y B radially inwards greater than force on Y C radially outwards less than force on Y D radially outwards greater than force on Y 3 The diagram below shows two small charged spheres P and Q of small mass which are hung by identical fine nylon threads from a fixed point X. It is found that, in equilibrium, the angle a is greater than the angle b. Which of the following statements must be correct? A The mass of P is less than that of Q. B The mass of P is greater than that of Q. C The charge of P is numerically smaller than that of Q. D The charge of P is numerically greater than that of Q. a b X P Q

9749 H2 Physics Tutorial w/ Solutions Topic 13: Electric Fields Page 3 of 22 4 Point charges, each of magnitude Q, are placed at three corners of a square as shown in the diagram. What is the direction of the resultant electric field at the fourth corner? 5 A charged particle is in the electric field between two horizontal metal plates connected to a source of constant potential difference, as shown. There is a force F on the particle due to the electric field. The separation of the plates is doubled. What will be the new force on the particle? A F/4 B F/2 C F D 2F 6 A particle has a charge of 4.8 × 10 –19 C. The particle remains at rest between a pair of horizontal, parallel plates having a separation of 15 mm. The potential difference between the plates is 660 V. What is the weight of the particle? A 1.1 × 10−23 N B 2.1 × 10−17 N C 2.1 × 10−15 N D 2.1 × 10−14 N +Q +Q – Q A B C D

9749 H2 Physics Tutorial w/ Solutions Topic 13: Electric Fields Page 4 of 22 7 Four charges are arranged at the corners of a square as shown. Point P is located at the centre of the square. The diagonal of the square is 8.0 cm. How much work is done by the field in bringing a −3.0 nC charge from infinity to point P without an