Why a man in an insulated metal cage does not receive any shock when the cage is connected to a high voltage source ?

Ans : Shock is produced by current flowing through the body of a man . When the man is inside a cage , he is at the same potential as the cage itself , so no current flows through his body when he touches the cage .

A small sphere is charged to a potential of 50 V and a big hollow sphere is charged to a potential of 100 V . How can you make electricity flow from the smaller sphere to the bigger one ?

Ans : Place the smaller one inside the bigger one . As potential inside a hollow conductor is same as that of its surface , the potential inside the hollow conductor is now 100 V . The potential of the smaller conductor is now 100 + 50 = 150 V . Connect the two conductors by a wire . Charge will flow from the smaller one to the bigger one as the smaller one is at 150 V and the bigger one is at 100 V .

Can two equipotential surfaces intersect ?

Scientific Reasoning : Can two equipotential surfaces intersect ?

Ans : No , two equipotential surfaces can never intersect because if they intersect at a point , the electric field at a point can have two directions simultaneously , which is impossible .

Q . Ordinary rubber is an insulator . But the special rubber tyres of aircraft are made conducting . why is this necessary ?

Ans : To conduct away electricity produced by friction .

How can you check whether the electric potential in a given region of space has a constant value ?

Ans : Place two conductors some distance apart in a given region . Connect them by a wire and then remove it . Now test the two conductors for any charge on them . If they are found to carry no charge , it means that the electric potential in the given region of space is constant .