12th Class Physics Sample Paper Physics Sample Paper-7

  • question_answer
     The circuit in figure shows two cells connected in opposition to each other. Cell \[{{E}_{1}}\] is of emf 6V and internal resistance \[2\,\Omega \] the cell  is of emf 4V and internal resistances \[8\,\Omega .\] Find 
     (i) effective resistance of the circuit
    (ii) effective emf of the two cells and current in the circuit
    (iii) the potential difference between the points A and B.


    (i) Consider the given circuit as shown below, Effective resistance \[2\,\Omega +8\,\Omega =10\,\Omega \] (ii) Effective emf of two cells \[=6-4=2\text{ }V,\] so the electric current is given by \[\Rightarrow \]   \[I=2/10=0.2\,A\] along anti-clokwise direction, since \[{{E}_{1}}>{{E}_{2}}.\] (iii) The direction of flow of current is always from high potential to low potential. Therefore, \[{{V}_{B}}>{{V}_{A}}.\] \[\Rightarrow \]   \[{{V}_{B}}-4V-(0.2)\times 8={{V}_{A}}\] Therefore,          \[{{V}_{B}}-{{V}_{A}}=5.6V\]

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