A network of four capacitors of capacity equal to C1 = C , C2 = 2C , C3 = 3C and C4 = 4C are connected to a battery as shown in the figure. The ratio of the charges on C2 and C4 is ?

As per the diagram, a point charge +q is placed at the origin O. Work done in taking another point charge −Q from the point A[ coordinates (0, a)] to another point B [coordinates (a, 0)] along the straight path AB is ?

Two charges q1 and q2 are placed 30 cm apart, as shown in the figure. A third charge q3 is moved along the arc of a circle of radius 40 cm from C to D. The change in the potential energy of the system is q3/4πε0 k, where k is ?