Question

A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R', then the ratio R/R' is −

(a)

(b)

(c) 5

(d) 25

Answer 1

(d) Resistance of a piece of wire is proportional to its length. A piece of wire has a resistance R. The wire is cut into five equal parts.

Therefore, resistance of each part =

All the five parts are connected in parallel. Hence, equivalent resistance (R’) is given as

Therefore, the ratio is 25.