Consider three capacitors of capacitance C1, C2, and C3 connected in series with a battery of voltage V as shown in figure (a). As soon as the battery is connected to the capacitors in series, the electrons of charge -Q are transferred from the negative terminal to the right plate of C3 which pushes the electrons of the same amount -Q from a left plate of C3 to the right plate of C2 due to electrostatic induction. Similarly, the left plate of C2 pushes the charges of Q to the right plate of which induces the positive charge +Q on the left plate of C1 At the same time, electrons of charge -Q are transferred from the left plate of C1 to the positive terminal of the battery.
