Question

please solve this question

Answer 1

We know that potential energy of a dipole is given by
U = -pEcos∅ { p = q×d
so here p = ±8×10^-9 × 4×10^-2
=> p = 32×10^-11

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here ∅ = 60°
l = 4cm
torque = 4√3N
charge = ±8nC


Now torque is given by pEsin∅
=> torque = 32×10-¹¹ ×√3/2 × E
=> 4√3 =16√3 ×10-¹¹ × E
=> E = 1/4 × 10¹¹

so U = +32×10-¹¹×1/4×10¹¹ cos60°
=> U= -8×1/2 => -4 Joule