question_answer

In the adjoining figure the equivalent resistance between A and B is

A)  50                                         

B)  80

C)  2.50                                      

D)  6.80

E)  7.80

Correct Answer: A

Solution :

                Equivalent circuit of the given circuit is Between points C and D resistors 2\[\Omega \], 2\[\Omega \] and 2\[\Omega \] are in series, therefore their equivalent resistance, \[R=2+2+2=6\,\Omega \] Resistors\[R\]and \[6\,\Omega \] are in parallel, therefore their equivalent resistance is given by \[\frac{1}{R\,\,}=\frac{1}{6}+\frac{1}{6}\] \[R\,\,=3\Omega \] Now between points A and B 1\[\Omega \], 3\[\Omega \] and 1\[\Omega \] are in series. Therefore, resultant resistance is \[R=1+3+1=5\Omega \]