Monday, 4 April 2016



1. Two charges +q and –q are located at points A (0,0,-2) and B(0,0,2) respectively How much work will be done in moving a test charge form point P(4,0,0) to Q(-5,0,0)

2.If 100J of work must be done to move electric charge =4C from a place where potential is -10 V to another place where potential is V volt, find the value of V.
VA – VB = WAB/q The value of V is 15 V.

3.If 10J of work is to be done in moving a charge of -200C from A to B., which of the 2 points is at higher potential? What is potential difference?
A; -0.05V

4. Two point charges of 4μC and -2μC are separated by a distance of 1m in air. Calculate at what point on the line joining the 2 charges is the electric potential zero?
2/3 m from 4 C

5. What is potential at the centre of a square of each side 1.0m when 4 charges +1 x 10 -8C, -2 x10 -8 ,
+3 x10 -8 and +2 x 10-8 C are placed at 4 corners of the square.
potential is 5.1 x 102 V

6. A point charge of 10 -8 C is situated at the origin of coordinates. Find the potential difference between the point A (4, 4,2) and B(1,2,2).
potential is -15 V

7. 27 charged water droplets each with diameter of 2mm and a charge of 10 -12 C coalesce to form a single drop. Calculate the potential of bigger drop.
Potential of the bigger drop is 81 V

8.An electric field E = (20i+30j)N/C. exist in the space. If the potential at the origin is taken to be 0 , find the potential at (2m,2m) .
potential at (2m, 2m) is -100 V

9.Two point Charges of A and B of value +15μC and +9μC are kept 18cm apart in air. Calculate the work done when charge B is moved by 3 cm toward A.
Work done is 1.35 J

10.2 electrons each moving with a velocity of 10 6 m/s are released towards each other. What will be the closest distance of approach between them?
2.56 x 10-10 m

11. Setup an arrangement of 3 point charges +q , +2q and xq are separated by equal finite distances so that electric PE of the system is 0. What is x?
Charges +q, +2q and -2q/3 at vertices of an equilateral triangle; x = -2/3

12. Three charges –q ,Q and –q are placed at equal distances on a straight line. If the potential Energy of system of 3 charges is 0 then what is the ratio of Q: q?