Solve this : 53 Figure shows a circuit with known resistance R1 R2 Neglect the - Physics - Current Electricity

Question

Solve this :

53 Figure shows a circuit with known resistance R1 &
R2 Neglect the internal resistance of the sources of the
current and resistance of the connecting wire The magnitude of
electromotive force E1 such that the current through the
resistance R is zero will be

a )   E R 1 / R 2            
                 
              B )    
E R 2 / R 1                
                 
  C )     E ( R 1 + R 2 ) R 2      
                 
  D )     E R 1 R 1 + R 2

Sanjay Singh · Accepted Answer

Dear student
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Let potential of negative terminal of the cell with emf E is zero   that is of point A is zero so potentia of different points are as VB=E    VC=E     Vd=-E1as there is no current in resistor across BE so potential of point B and E is same
VB=VC=EApplying Kirchoffs junction rule at the junction Cnet current diverging  from point E is zero
Current in CB+Current in CD+current in EF=00+E-(-E1)R1+E-0R2=0E+E1R1=-ER2R2(E+E1)=-E×R1ER2+E1R1=-E×R1E1R1=-E×R1-ER2E1=(-E×R1-ER2)R1=-E(R1+R2)R1magnitude of E1 isE1=E(R1+R2)R1Regards