Question

The infinity resistance plug in a post-office box has
(A) An air gap only
(B) A resistance coil of infinite resistance
(C) Largest resistance available in box
(D) Resistance of the coil 5000

Answer 1

Hint It should be known to us that a plug is a resistance box, which on being pulled out will result in the seat opening the circuit making it of infinite resistance. Having an idea about the post- office box will help us to answer this required question.

Complete step by step answer
It is known as when the infinity plug is taken out, an air gap is introduced in the circuit. Since we know that air is a bad conductor of current, no current flows in the circuit which implies infinity resistance is introduced in the circuit.

Note The post-office box is called so because of the shape of the box which is resembling the design of a post-office box. It is used to find the resistance of electric cables and telegraph wires. Earlier it was used in the post offices to determine the resistance of transmission lines.
The resistance box is also defined as the box that contains the resistors of different values which are used for estimating and comparing the resistance. The main plus point of using the resistance box is that the accuracy of measuring the resistance is very high. The main advantage of using the resistance box is that the variable resistances are all present at a single point.