Q90 / 180 · JIPMER 2018 · Physics

If point charges $\mathrm{Q}_1=2 \times 10^{-7} \mathrm{C}$ and $\mathrm{Q}_2=3 \times 10^{-7} \mathrm{C}$ are at 30 cm separation, then find electrostatic force between them

  • A
    $2 \times 10^{-3} \mathrm{~N}$
  • Correct answer
    B
    $6 \times 10^{-3} \mathrm{~N}$
  • C
    $5 \times 10^{-3} \mathrm{~N}$
  • D
    $1 \times 10^{-3} \mathrm{~N}$

Solution

$\because$ Electrostatic force, $\mathrm{F}=\mathrm{k} \frac{\mathrm{Q}_1 \mathrm{Q}_2}{\mathrm{r}^2}$ $=9 \times 10^9 \times \frac{2 \times 10^{-7} \times 3 \times 10^{-7}}{\left(30 \times 10^{-2}\right)^2}=6 \times 10^{-3} \mathrm{~N}$

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

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