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An electric dipole with dipole moment 4 × 10^{−9} C m is aligned at 30° with the direction of a uniform electric field of magnitude 5 × 10^{4} N C^{−1}. Calculate the magnitude of the torque acting on the dipole.

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#### Solution

Electric dipole moment, p = 4 × 10^{−9} C m

Angle made by p with a uniform electric field, θ = 30°

Electric field, E = 5 × 10^{4} N C^{−1}

Torque acting on the dipole is given by the relation,

τ = pE sinθ

= `4 xx 10^-9 xx 5 xx 10^4 xx sin30`

= `20 xx 10^-5 xx 1/2`

= `10^-4 "N m"`

Therefore, the magnitude of the torque acting on the dipole is 10^{−4} N m.

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