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Question
An electric dipole is placed at an angle of 30° with an electric field intensity of 2 × 105 N/C. It experiences a torque equal to 4 Nm. The charge on the dipole, if the dipole length is 2 cm, is ______.
Options
7 μC
8 mC
2 mC
5 mC
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Solution
An electric dipole is placed at an angle of 30° with an electric field intensity of 2 × 105 N/C. It experiences a torque equal to 4 Nm. The charge on the dipole, if the dipole length is 2 cm, is 2 mC.
Explanation:
We know,
τ = pE.sinθ
∴ p = `tau/("E".sintheta)`
q × 2l = `4/(2 xx 10^5 xx 0.5)` ............(∵ p = q × 2l)
∴ q = `4/(2 xx 10^5 xx 0.5 xx 0.02)` ....(∵ 2l = 0.02m given)
= 2 × 10-3 C
q = 2 mC
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