Chapter 10: Electrostatics - Answers

Chapter 10: Electrostatics EXERCISES IPAGES 205-2061 Exercises | Q1. (0| Page 205 Choose the correct option. A positively charged glass rod is brought close to a metallic rod isolated from ground. The charge on the side of the metallic rod away from the glass rod will be 1. same as that on the glass rod and equal in quantity 2. opposite to that on the glass of and equal in quantity 3. same as that on the glass rod but lesser in quantity 4. same as that on the glass rod but more in quantity SOLUTION Same as that on the glass rod and equal in quantity Exercises | Q1. ()| Page 205 Choose the correct option. An electron is placed between two parallel plates connected to a battery. If the battery is switched on, the electron will 1. be attracted to the ve plate 2. be attracted to the-ve plate 3. remain stationary 4. will move parallel to the plates SOLUTION An electron is placed between two parallel plates connected to a battery. If the battery is switched on, the electron will be attracted to the + ve plate Exercises | Q1.() | Page 205 Choose the correct option. A charge of +7 µC is placed at the centre of two concentric spheres with radius 2.0 cm and 4.0 cm respectively. The ratio of the flux through them will be 1. 1:4 2. 1:2 3. 1:1 4. 1:16 SOLUTION 1:1 Explanation: The total flux is independent of shape and radius. Exercises Q1. (iv) | Page 205 Choose the correct option. Two charges of 1.0 C each are placed one meter apart in free space. The force between them will be 1. 1.0N 2.9 x 10 N 3.9 × 10N 4. 10N SOLUTION 9 x 109 N Explanation: F= 1992 -9x 109 x 1x1 1 = 9 × 109 N Exercises | Q1. (v) | Page 205 Choose the correct option. Two point charges of +5 µC are so placed that they experience a force of 8.0 × 10N. They are then moved apart so that the force is now 2.0 x 10 N. The distance between them is now 1. 1/4 the previous distance 2. double the previous distance 3. four times the previous distance 4. half the previous distance SOLUTION double the previous distance Explanation: Fconlomba 8×10-3 2 × 10-3 -4x 12=2r1 Exercises | Q1. (vi) | Page 205 Choose the correct option. A metallic sphere A isolated from ground is charged to +50 µC. This sphere is brought in contact with other isolated metallics sphere B of half the radius of sphere A. The charge on the two-sphere will be now in the ratio 1. 1:2 2. 2:1 3. 4:1 4. 1:1 SOLUTION 1:1 Explanation: When two conductors, one charged and the other uncharged are brought in contact with each other, the charge (whether-ve or +ve) under its own repulsion will spread over both the conductors. Thus, the conductors will be charged uniformly with the same sign. Exercises | Q1. (vi) | Page 206 Choose the correct option. Which of the following produces uniform electric field? 1. point charge 2. linearcharge 3. two parallel plates 4. charge distributed an circular any SOLUTION Two parallel plates Exercises | Q1. (viii) | Page 206 Choose the correct option. Two-point charges of A = +5.0 µC and B = -5.0 µC are separated by 5.0 cm. A point charge C = 1.0 µC is placed at 3.0 cm away from the centre on the perpendicular bisector of the line joining the two point charges. The charge at C will experience a force directed towards 1. point A 2. point B 3. a direction parallel to line AB 4. a direction along the perpendicular bisector SOLUTION A direction parallel to line AB Explanation: The situation resembles a point along the equatorial line of a dipole. Therefore, force- directed would be along a direction parallel to line AB. Exercises | Q2. (1) | Page 206 Answer the following question. What is the magnitude of the charge on an electron? SOLUTION The magnitude of the charge on an electron is 1.6 x 10-1 C. Exercises | Q2. (ii)| Page 206 Answer the following question. State the law of conservation of charge. SOLUTION In any given physical process, "the charge may get transferred from one part of the system to another, but the total charge in the system remains constant OR For an isolated system, total charge cannot be created nor destroyed, Exercises | Q2. (iii) | Page 206 Answer the following question. Define a unit charge. SOLUTION Unit charge (one coulomb) is the amount of charge which, when placed at a distance of one meter from another charge of the same magnitude in a vacuum, experiences a force of 9.0 x 10 N. Exercises | Q2. (iv) | Page 206 Answer the following question. Two parallel plates have a potential difference of 10V between them. If the plates are 0.5 mm apart, what will be the strength of the electric charge. SOLUTION Given: V = 10 V, d = 0.5 mm 0.5×10-3 m To find: Strength of electric field (E) V Formula: E- Calculation: From the formula, E= 10 0.5 × 10-3 = 20 × 103 V/m The strength of the electric field will be 20 x 10³ V/m Exercises | Q2. (v) | Page 206 Answer the following question. What is a uniform electric field?