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# Solve this problem An electric dipole is placed at an angle of 30° with an electric field intensity2 x 105 N/C. It experiences a torque equal to 4 N m. The charge on thedipole, if the dipole length is 2 cm, is

An electric dipole is placed at an angle of 30° with an electric field intensity 2 x 105 N/C. It experiences a torque equal to 4 N m. The charge on the dipole, if the dipole length is 2 cm, is

• Option 1)

8 mC

• Option 2)

2 mC

• Option 3)

5 mC

• Option 4)

7 C

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As we discussed in

Torque Experienced by the dipole -

$\dpi{100} \vec{\tau }=\vec{P}\times \vec{E}$

$\dpi{100} \vec{\tau }=PE\sin \Theta$

$\dpi{100} \Theta =0^{\circ}$    $\dpi{100} \tau =0$

$\dpi{100} \Theta =\frac{\pi }{2}$             $\dpi{100} \tau = max^{m}$

- wherein

$T=PESin\theta\:\:\:\:\:\:=> (ql)ESin\theta$

$q=\frac{T}{ElSin\theta}\:\:\:\:\:=\frac{4}{2\times10^{5}\times0.02\times\frac{1}{2}}$

$\frac{4}{2\times10^{3}}=2\times10^{-3}=2mC$

Option 1)

8 mC

This option is incorrect.

Option 2)

2 mC

This option is correct.

Option 3)

5 mC

This option is incorrect.

Option 4)

7 C

This option is incorrect.

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