Two point charges +2 C and -2 C are placed at the coordinates (0, 2 cm , 0) and (0, -2 cm , 0) respectively. If this electric dipole is placed in a uniform electric field E = 5 10^5 i N C ⁻¹ , what is the torque vector experienced by the dipole?

Step-by-step solution

The electric dipole moment p is a vector directed from the negative charge to the positive charge. Position of -q is (0, -2 cm , 0) and position of +q is (0, 2 cm , 0) . The displacement vector d from -q to +q is: d = (2 - (-2)) j cm = 4 j cm = 0.04 j m The dipole moment p is: p = q d = (2 10⁻⁶ C ) (0.04 j m ) = 8 10⁻⁸ j C m The electric field is given as E = 5 10^5 i N C ⁻¹ . The torque experienced by the dipole is the cross product of p and E : = p E = (8 10⁻⁸ j ) (5 10^5 i ) = (8 5 10⁻³) ( j i ) = 40 10⁻³ (- k )