question_answer

What is the resistance between the X and Y of the circuit in the figure ? that the resistance of each resistor 25\[\Omega \] .

A)  100 \[\Omega \]                             

B)  50\[\Omega \]

C)  25 \[\Omega \]                                

D)  75\[\Omega \]

Correct Answer: C

Solution :

                The given circuit can be drawn as follows : Since, ratio of resistances in the opposite arms of the bridge is same, hence, it is a balanced Wheatstone bridge. Therefore, arm BD is ineffective. The circuit now reduces as follows: We have two resistors of\[2R\,\Omega \]. Each connected in parallel. Hence, resultant resistance is \[\frac{1}{R}=\frac{1}{2R}+\frac{1}{2R}=\frac{2}{2R}\]\[\Rightarrow \]    \[R-R=25\,\Omega \]