question_answer

Two resistors of resistances\[200\,k\Omega \]and\[1\,M\Omega \] respectively form a potential divider with outer junctions maintained at potentials of\[+3V\]and\[-15V\]. Then, the potential at the junction between the resistors is

A)  \[+1\text{ }V\]                                

B)  \[-0.6\text{ }V\]

C)  zero                     

D)         \[-\,12V\]

E)  \[+12\text{ }V\]

Correct Answer: C

Solution :

Current \[i=\frac{{{V}_{1}}-{{V}_{2}}}{{{R}_{1}}+{{R}_{2}}}=\frac{18}{1.2\times {{10}^{-6}}}\] V across \[1\,M\Omega =\frac{18}{1.2\times {{10}^{-6}}}\times 1\times {{10}^{-6}}\]                                 \[=15\,V\] \[\therefore \]Potential at \[P=15-15=0\]