Question

20. An electric dipole consists of two opposite charges
each of magnitude 1uC separated by a distance of
2 cm. The dipole is placed in an external field of
105 N/C. The maximum torque on the dipole is
(1) 2 x 106 Nm (2) 2 x 10-3 Nm
(3) 4 x 10-3 Nm (4) 10-3 Nm​

Answer 1

Given :-

• An electric dipole consists of two opposite charges each of magnitude 1uC (q) separated by a distance of 2 cm (d).

• Intensity of the external electric field (E) = 10^5 N/C

To Find :-

• Maximum torque.

Solution :-

We know maximum torque :-

$\bf\tau_{max} = PE$

Here,

$\bf P = q \times 2d$

• q =  $\sf1 \times 10^{-6} C$
• d = $\sf 2 \times 10^{-2} m$
• E = $\sf 10^5 N/C$

By substituting the given date, we get :-

$: \implies \sf \tau_{max} = 1 \times {10}^{ - 6} \times 2 \times 2 \times {10}^{ - 2} \times {10}^{5}$

$: \implies \sf \tau_{max} = 4 \times {10}^{ - 6 - 2 + 5}$

$: \implies \underline{\underline{\bf \tau_{max} = 4 \times {10}^{ - 3} } }$

Option 3 is correct.