Question

the magnitude of charge in a dipole is 3.2×10^-19 c and their separation is 2.4 armstrong if the dipole is placed perpendicular in a uniform electric field of intensity 4×10^5 n/c the torque acting on the dipole is about ______________
(a) 3x10^-23 Nm
(b) 3x10^23 Nm
(c) 4x10^-23 Nm
(d) 4x10^23 Nm

Answer 1

Wonderful Question.

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Magnitude of each charges = 3.2 × 10⁻¹⁹ C.

Separation between them = 2.4 Angstrom.

Dipole moment = Magnitude of charge × Separation between the two charges.

= 3.2 × 10⁻¹⁹ × 2.4 × 10⁻¹⁰

= 7.68 × 10⁻²⁹ Cm.

Now, The angle between the electric flied and dipole is 90⁰.

Now, using the formula of the Torque,

τ = p × E

τ = pESinθ

τ = 7.68 × 10⁻²⁹ ×  4 × 10⁵

τ = 3.072 × 10⁻²³

τ ≈ 3 × 10⁻²³ Nm.

Hence, Option (a). is Correct.

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Hope it helps.