Question

Two point charges + 3 mC and + 8 mC repel each other with a force of 40 N. If a charge of –5 mC is added to each of them, then the force between them will become -

• A.
  • 10 N
• B.
  • 20 N
• C. – 20 N
• D. – 10 N

Answer 1

Answer: (D)

– 10 N

Answer 2

F = F ¢ = $\frac { 6 \mathrm {~K} } { \mathrm { r } ^ { 2 } }$

$\frac { \mathrm { K } } { \mathrm { r } ^ { 2 } } = \frac { 40 } { 24 }$ = $6 \times \frac { 40 } { 24 }$= 10 N

Now the force will be attraction