question_answer

Voltmeters V1 and V2 are connected in series across a D.C. line.  V1 reads 80 volts and has a per volt resistance of 200 ohms.  V2 has a total resistance of 32 kilo ohms.  The line voltage is                                           [UPSEAT 2000]

A)         120 volts

B)         160 volts

C)         220 volts                         

D)         240 volts

Correct Answer: D

Solution :

                                         \[{{R}_{1}}=80\times 200=16000\,\Omega =16\,k\Omega \] Current flowing through \[{{V}_{1}}\]= Current flowing through \[{{V}_{2}}\] = \[\frac{80}{16\times {{10}^{3}}}=5\times {{10}^{-3}}A\]. So, potential differences across \[{{V}_{2}}\] is \[{{V}_{2}}=5\times {{10}^{-3}}\times 32\times {{10}^{3}}=160\,\text{volt}\] Hence, line voltage \[V={{V}_{1}}+{{V}_{2}}=80+160=240V\].