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Question
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.
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Solution
Given:
E1=1.5 V
E2=2 V
r1=0.2 Ω
r2 =0.3 Ω
The effective emf of two cells connected in parallel can be calculated as follows:
`E_(eff) = (E_1r_2+E_2r_1)/(r_1+r_2)`
`=> E_(eff) = (1.5xx0.3+2.0xx0.2)/0.5 = 1.7 V`
The effective resistance can be calculated as follows:
`R_(eff)= (r_1r_2)/(r_1+r_2)`
`=> R_(eff)= (0.2xx.03)/0.5`= 0.12 Ω
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