Physics books
Q 1.1) What is the force between two small charged spheres having charges of 2 × 10 –7 C and 3 × 10 –7 C placed 30 cm apart in the air? Soln: Given, The Charge on the 1 st sphere and 2 nd sphere is q 1 = 2 x 10 -7 C and q 2 = 3 x 10 -7 C The distance between two charges is given by r = 30cm = 0.3m The electrostatic force between the spheres is given by the relation : F = \frac{1}{4\pi \epsilon _{o}}.\frac{q_{1}q_{2}}{r^{2}} 4 π ϵ o 1 . r 2 q 1 q 2 Here, \epsilon _{o} ϵ o = permittivity of free space and, \frac{1}{4\pi \epsilon _{o}} 4 π ϵ o 1 = 9 x 10 9 Nm 2 C -2 Force, F = \frac{9 \times 10^{9} \times 2 \times 10^{-7} \times 3 \times 10^{-7}}{(0.3)^{2}} ( 0 . 3 ) 2 9 × 1 0 9 × 2 × 1 0 − 7 × 3 × 1 0 − 7 = 6 x 10 ‑3 N. The force between the charges will be repulsive as they have the same nature. Q 1.2) The electrostatic force on a small sphere of charge 0.4 µC due to another small sphere of charge –0.8 µC in the air is 0.2 N. (a) What is the distanc