ElectrostaticsHard
Question
Two opposite and equal charges of magnitude 4 × 10-8 coulomb each when placed 2 × 10-2 cm apart form a dipole. If this dipole is placed in an external electric field of 4 × 108 N/C, the value of maximum torque and the work required in rotating it through 180o from its initial orientation which is along electric field will be : (Assume rotation of dipole about an axis passing through centre of the dipole):
Options
A.64 × 10-4 N-m and 44 × 10-4 J
B.32 × 10-4 N-m and 32 × 10-4 J
C.64 × 10-4 N-m and 32 × 10-4 J
D.32 × 10-4 N-m and 64 × 10-4 J
Solution
= 4 × 10-8 × 2 × 10-4 × 4 × 108 = 32 × 10-4 N-m.
Work done W = (P.E.)f – (P.E.)i = PE − (−PE) = 2PE = 64 × 10-4 N-m
Work done W = (P.E.)f – (P.E.)i = PE − (−PE) = 2PE = 64 × 10-4 N-m
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