Question

Two equal metal balls are charged to $10$ and $20$ units of electricity. They are brought in contact with each other and then again separated to the origin distance. The ratio of forces between the two balls before and after contact is :

• A. $3:2$
• B. $1:8$
• C. $2:3$
• D. $8:9$

Answer 1

Answer: (D)

$8:9$

Charge is conserved so
$Q1+Q2=Q3+Q4$
$Q1$ and $Q2$ are initial charges and $Q3$ and $Q4$ are charges after connecting them
$Q3=Q4=Q$ ( they are identical )
So $Q=$ $\frac{10+20}{2}$
$Q=15C$
Ratio of forces $=K\left(10\right)\left(20\right):K\left(15\right)\left(15\right)$
$8:9$