The electric field intensity at the mid point of a dipole with charge ±q and dipole length 2a is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \( \displaystyle\frac{1}{4\pi\varepsilon_0}\frac{2q}{a^{2}} \)
By the superposition principle the field at the midpoint is the vector sum of the fields of the two charges. Each charge is at distance a from the midpoint.
The field of \( +q \) points away from it, towards \( -q \). The field of \( -q \) points towards it, also towards \( -q \). The two fields therefore point in the same direction and add.
\( \displaystyle E = \frac{1}{4\pi\varepsilon_0}\frac{q}{a^{2}}+\frac{1}{4\pi\varepsilon_0}\frac{q}{a^{2}} = \frac{1}{4\pi\varepsilon_0}\frac{2q}{a^{2}} \)