CBSE Class 12 Physics 2016 Delhi Set 1 Paper

Question : 9 of 26

Marks: +1, -0

Two cells of emfs

1.5 {\V}

and

2.0 {\V}

having internal resistances

0.2 Ω

and

0.3 Ω

respectively are connected in parallel. Calculate the emf and internal resistance of the equivalent cell.

Solution:

Calculation of emf
Calculation of internal resistance

\;\text " E. M. F "\;

\;=\;{E_{12} r_2+E_{21}}/{r_1+r_2}

\;=\;{1.5 × 0.3+2 × 0.2}/{0.2+0.3} {\V}

\;=\;{0.45+0.40}/{0.5} {\V}=1.7 {\V}

r\;=\;{r_1 r_2}/{r_1+r_2}

\;=\;{0.2 × 0.3}/{0.2+0.3} Ω

\;=\;{0.06}/{0.5} Ω

\;=0.12 Ω

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