Question

Two identical small conducting balls B₁ and B₂ are given −7 pC and + 4 pC charges respectively. They are brought in contact with a third identical ball B₃ and then separated. If the final charge on each ball is −2 pC, the initial charge on B₃ was ______.

Options

• −2 pC

• −3 pC

• −5 pC

• −15 pC

Answer 1

Two identical small conducting balls B₁ and B₂ are given −7 pC and + 4 pC charges respectively. They are brought in contact with a third identical ball B₃ and then separated. If the final charge on each ball is −2 pC, the initial charge on B₃ was −3 pC.

Explanation:

Charge is conserved. Final total charge =3 × (−2) = −6 = 3.

Initial total = −7 + 4 + q3 = −3 + q3.

So −3 + q3 = −6 ⇒ q3 = −3 pC.