# Two point charges 5μC and 4μC are 10 cm apart. Find the force by which they will repel each other.

29 views
in Physics
closed
Two point charges 5μC and 4μC are 10 cm apart. Find the force by which they will repel each other.
1. 10 N
2. 36 N
3. 18 N
4. 9 N

by (55.2k points)
selected

Correct Answer - Option 3 : 18 N

CONCEPT:

• Coulomb’s law is an inverse square law of force that describes the electrostatic force between charged particles.
• Electrostatic Force: between two charges q1 and q2 at the distance of R is given by:

$F=\frac{1}{4\pi ϵ_0}\frac{q_1q_2}{R^2}$

where F is the electrostatic force, q1 and qare the charges, and ϵ0 is the electrical permittivity of the vacuum.

CALCULATION:

Given that q1 = 5μC and q2 = 4μC R = 10cm = 0.1m;

We know $F=\frac{1}{4\pi ϵ_0}\frac{q_1q_2}{R^2}$

$F=9×10^9×\frac{5μC \times 4μC}{0.1^2}$

$F=9×10^9×\frac{5​​​​ \times 10^{-6} \times 4 \times 10^{-6}}{0.1^2} =18$

F = 18 N

So the correct answer is option 3.