Two point charges +3 and +8 repel each other with a force of 40 N. If a charge of -5 is added to each of them, then force between them will become (a) - 10 N (b) 10 N (c) 20 N (d) - 20 N

Answer: (a). F ∝ q₁q₂: initially q₁q₂ = 3 × 8 = 24 ()² gives 40 N. New charges: 3 - 5 = -2 and 8 - 5 = +3, product = -6. F' = 40 × -6/24 = -10 N (negative sign means attraction). So the answer is (a) -10 N.

Two point charges +3 and +8 repel each other with a force of 40 N. If… | MHT CET 2021 (23 Sep, Shift 2)

Q57MHT CET 2021 · 23 SEP · SHIFT 2Medium

Electric Charge & Coulomb's Law

Two point charges $+3\ \mu\text{C}$ and $+8\ \mu\text{C}$ repel each other with a force of $40\text{ N}$ . If a charge of $-5\ \mu\text{C}$ is added to each of them, then force between them will become

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Answer: (a)

$F \propto q_1q_2$ : initially $q_1q_2 = 3 \times 8 = 24\ (\mu\text{C})^2$ gives $40\text{ N}$ .
New charges: $3 - 5 = -2\ \mu\text{C}$ and $8 - 5 = +3\ \mu\text{C}$ , product $= -6$ .
$F' = 40 \times \dfrac{-6}{24} = -10\text{ N}$ (negative sign means attraction).
So the answer is (a) $-10$ N.

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Electric Charge & Coulomb's Law question from MHT CET 2021 (23 Sep, Shift 2)

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