Consider two infinitely large plane parallel conducting plates as shown below. The plates are uniformly charged with a surface charge density $+\sigma$ and $-2 \sigma$. The force experienced by a point charge +q placed at the mid point between two plates will be :

• A

  $\frac{\sigma q}{4 \epsilon_0}$
• Correct answer
  B

  $\frac{3 \sigma q}{2 \epsilon_0}$
• C

  $\frac{3 \sigma q}{4 \in_0}$
• D

  $\frac{\sigma q}{2 \epsilon_0}$

Solution

Final charge distribution will be
$\therefore \mathrm{F}_{\mathrm{net}}=\frac{3 \sigma}{2 \epsilon_0} \mathrm{q}$

Hence, the correct answer is option: 'B'.