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Question:

Two metallic spheres of radii 1cm and 3cm are given charges of 5×10⁻⁶C and 5×10⁻⁶C, respectively. If these are connected by a conducting wire, the final charge on the bigger sphere is?

3×10⁻⁶C

4×10⁻⁶C

1×10⁻⁶C

2×10⁻⁶C

Solution:

Qtotal=5×10⁻⁶C + 5×10⁻⁶C=4×10⁻⁶C
We know that,
Charge distribution ∝ radius
∴Qsmall:Qbig=1:3
Qbig=3/4 × 4 ×10⁻⁶ =3×10⁻⁶C