Question

Two electric dipoles of moment P and 64 P are placed in opposite direction on a line at a distance of 25 cm. The electric field will be zero at point between the dipoles whose distance from the dipole of moment P is

• A. 5 cm
• B. $\frac{25}{9}$cm
• C. 10 cm
• D. $\frac{4}{13}$ cm

Answer 1

Answer: (A)

5 cm

Answer 2

Suppose neutral point N lies at a distance x from dipole of moment p or at a distance x₂ from dipole of 64 p.

At N |E. F. due to dipole ①|= |E. F. due to dipole ②|

⇒ $\frac{1}{4\pi\varepsilon_{0}}.\frac{2p}{x^{3}} = \frac{1}{4\pi\varepsilon_{0}}.\frac{2(64p)}{(25 - x)^{3}}$

⇒ $\frac{1}{x^{3}} = \frac{64}{(25 - x)^{3}}$ ⇒ x = 5 cm.