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 121, then the ratio R/R' is - (a) 1/25 (b) 1/5 (c) 5 (d) 25

Answer 1

We know, the resistance of a wire varies with length and is proportional.

If R is the resistance of the wire and it is cut into 5 pieces, therefore, the resistance is divided and becomes R/5 in each piece.  

Now the pieces are connected in parallel.

Therefore the equivalent resistance is 1/R = 5(5/R) = 25/R.  

Therefore R/R = 25 which is the ratio.  

Answer 2

your correct option is d

25