NEET2014PhysicsElectrostaticsActual
Three points charges +q,-2 q and +q are placed at points (x=0, y=a, z=0),(x=0, y=0, z=0) and (x=a, y=0, z=0) , respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are
Options
- A2 q a along +y direction
- B2 q a along the line joining points (x=0, y=0, z=0) and (x=a, y=a, z=0)
- Cqa along the line joining points (x=0, y=0, z=0) and (x=a, y=a, z=0)
- D2 q a along +x direction
Correct answer
B. 2 q a along the line joining points (x=0, y=0, z=0) and (x=a, y=a, z=0)
Step-by-step solution
O is the origin at which -2 q charge is placed. The system is equivalent to two dipoles along x and y -directions respectively. The dipole moments of two dipoles are shown in figure. The resultant dipole moment will be directed along O P where P=(a, a, 0) . The magnitude of resultant dipole moment is p^ = p^2+p^2 = (q a)^2+(q a)^2 = 2 q a