question_answer 1)

Two charges 5 × 10?8 C and ?3 × 10?8 C are located 16 cm apart. At what point(s) on the line joining the two charges is the electric potential zero? Take the potential at infinity to be zero.  

Answer:

Let the potential be zero at O, then                 VA + VB = 0,                                 where  is electric potential due to charge  and  is the electric potential due to charge .                  i.e.                 i.e.                 i.e.                 i.e. 5(0.16 ? x) = 3x                          i.e. 0.8 = 3x + 5x = ?8x                 or x = 0.1 m = 10 cm.                 Now taking the second case i.e. when                 x2 = 0.16 + x, we have                                 or                                                                  i.e. 5x = 3x ? 0.8                                 i.e. x = 0.4 m = 0.4 × 100 = 40 cm.                               i.e. electric potential is also zero at a distance of 40 cm from the charge q1.