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Two identical small conducting balls \(B _1\) and \(B _2\) are given -7 pC and +4 pC charges respectively. They are brou…

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Two identical small conducting balls \(B _1\) and \(B _2\) are given -7 pC and +4 pC charges respectively. They are brought in contact with a third identical ball \(B _3\) and then separated. If the final charge on each ball is -2 pC , the initial charge on \(B_3\) was

a

-2 pC

b

-3 pC

c

-5 pC

d

-15 pC

✓ Correct answer: b)

-3 pC

Explanation

Concept Used-Charge Redistribution

\({Q}_{T}\)=\({Q}_{1}\)\(+\)\({Q}_{2}\)\(+\)\({Q}_{3}\)

\({Q}_{T}\)= -7+4+\({Q}_{3}\)\(\ldots \ldots\)(1)

after contact

\({Q}_{F}\)=\(\frac{{Q}_{T}}{3}\)= -2pc

\({Q}_{T}\)= -6pc \(\ldots \ldots\)(2)

-6= -7+4+\({Q}_{3}\)

\({Q}_{3}\)= -3pc

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