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Question
An electric dipole of length 2 cm is placed at an angle of 30° with an electric field 2 × 105 N/C. If the dipole experiences a torque of 8 × 10-3 Nm, the magnitude of either charge of the dipole is ______.
Options
4 µC
7 µC
8 mC
2 mC
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Solution
An electric dipole of length 2 cm is placed at an angle of 30° with an electric field 2 × 105 N/C. If the dipole experiences a torque of 8 × 10-3 Nm, the magnitude of either charge of the dipole is 4 µC.
Explanation:
Given:
θ = 30°, E = 2 × 105 N/C, τ = 8 × 10-3 Nm and 2a = 2 cm = 0.02 m
To find: Charge q = ?
We know that, τ = pE sinθ
= (q × 2a) E sinθ ....(∵ p = q × 20)
`q = tau/(2a.E sintheta)`
`q = (8 xx 10^-3)/(0.02 xx 2 xx 10^5 xx sin30^circ)`
= `400 xx 10^-3 xx 10^-5`
q = 4 µC
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