Answer first question

Dear student

There will be potential difference between the spheres due to the change in the radius .

Now let, after the charge transfer, final charges be q_​1 and q₂ 

$$\begin{gathered} Finally at equilibrium the potential between the spheres will be the same \\ {V}_1=V_2 \\ \frac{1}{4{\mathrm{\pi \epsilon }}_{\mathrm{o}}}\frac{q_1}{r_1}=\frac{1}{4{\mathrm{\pi \epsilon }}_{\mathrm{o}}}\frac{q_2}{r_2} which for r_1=5cm and r_2=10cm \boxed{q_2=2q_1} \\ Also \sin ce charge will be conserved net charge at the beginning and end will be the same. \\ \boxed{q_1+q_2=150\mu C} \\ Substituting q_2 we get 3q_1=150 or q_1=50\mu C so q_2=100\mu C \\ Therefore 25\mu C charge went from smaller to bigger so option is \left(A\right) \end{gathered}$$

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