Question

Two spheres $A$and $B$ of radius $4cm$ and $6cm$ are given charges of $80\mu c$ and $40\mu c$respectively. If they are connected by a fine wire, the amount of charge flowing from one to the other is

• A. $20\mu C$from $A$to $B$
• B. $16\mu C$ from $A$to $B$
• C. $32\mu C$from $B$ to $A$
• D. $32\mu C$ from $A$to $B$

Answer 1

Answer: (D)

$32\mu C$ from $A$to $B$

Answer 2

Total charge $Q = 80 + 40 = 120\mu C$. By using the formula $Q_{1} ⥂ ' = Q\left\lbrack \frac{r_{1}}{r_{1} + r_{2}} \right\rbrack$. New charge on sphere A is $Q_{A}^{'} = Q\left\lbrack \frac{r_{A}}{r_{A} + r_{B}} \right\rbrack = 120\left\lbrack \frac{4}{4 + 6} \right\rbrack = 48\mu C$. Initially it was $80\mu C$ i.e., $32\mu C$ charge flows from A to B.