Two point charges, $q_1= 3 μC$ and $q_2=-2 μC$, are placed 6 cm apart. The magnitude of the electric force between them is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 15 N
Given:
Charges: $q_1 = 3\ \mu\text{C} = 3 \times 10^{-6}\ \text{C}$, $q_2 = -2\ \mu\text{C} = -2 \times 10^{-6}\ \text{C}$
Distance: $r = 6\ \text{cm} = 0.06\ \text{m}$
Electric force between two point charges (Coulomb's law):
$F = k \frac{|q_1 q_2|}{r^2}$
$F = 9 \times 10^9 \cdot \frac{(3 \times 10^{-6}) (2 \times 10^{-6})}{(0.06)^2}$
$F = 9 \times 10^9 \cdot \frac{6 \times 10^{-12}}{0.0036}$
$F = 9 \times 10^9 \cdot 1.6667 \times 10^{-9} \approx 15\ \text{N}$
∴ Magnitude of electric force = 15 N