question_answer

Four wires having same length, diameter and material are connected in the form of a square. If the resistance of each wire is R, then resistance of combination across any two opposite ends is

A)  R                

B)  R/2

C)  R/4              

D)  None of these

Correct Answer: A

Solution :

 The resistance across the wire \[ABC=R+R\] \[=2R\] and the resistance of wire ADC is 2R ADC and ABC are in parallel \[\frac{1}{{{R}_{eff}}}=\frac{1}{2R}+\frac{1}{2R}\] \[\frac{1}{{{R}_{eff}}}=\frac{1+1}{2R}=\frac{2}{2R}\] \[{{R}_{eff}}=R\]