Three cells of emf E, 2E, and 5 hav...
Question
Three cells of emf E, 2E, and 5 having internal resistances r, 2r and 3r respectively are connected across a variable resistance R as shown in the figure. Find the
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Three cells of emf ( E, 2 E ) and ( 5 E ) having internal resistances ( r, 2 r ) and ( 3 r ) respectively are connected across a variable resistance ( R ) as shown in the figure. Find the expression for the current. Plot a graph for variation of current with ( R ).All India 2010 C

JEE/Engineering Exams
Physics
Solution
558
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Three cells of emf E, 2E, and 5 having internal resistances r, 2r and 3r respectively are connected across a variable resistance R as shown in the figure. Find the expression for the current.
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The current is ( I=frac{8 E}{6 r+R} )
Detail:
Given that,
Emf of first cell = E
Emf of second cell = ( 2 E )
Emf of third cell = ( 5 E )
Internal resistance of first cell = r
Internal resistance of second cell = ( 2 mathrm{r} )
Internal resistance of third cell = ( 3 r )
Variable resistance ( =mathrm{R} )
Now, the current
Current( =frac{text {total emf}}{text {Internalresistances}+text {variableresistance}} )
( I=frac{E+2 E+5 E}{r+2 r+3 r+R} )
( I=frac{8 E}{6 r+R} )
Hence, this is the required solution.

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