question_answer

Three equal resistances each of value R. are joined as shown in the figure. The equivalent resistance between M and N is             

A)  R                                           

B)  2R               

C)  R/2                                       

D)  R/3

Correct Answer: D

Solution :

All 3 resistances are in parallel.                 \[\therefore \]  By           \[\frac{1}{R}=\frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}}+\frac{1}{{{R}_{3}}}\]                 or            \[\frac{1}{{{R}_{eq}}}=\frac{1}{R}+\frac{1}{R}+\frac{1}{R}\]                 \[\Rightarrow \]               \[{{R}_{eq}}=\frac{R}{3}\]