Question

Two cells of emf 3v and 2v and internal resistance 1.5 ohm and 1 ohm respectively are connected in parallel so as to send current in the same direction through an external resistance of 3 ohm.Find the potential difference across 3 ohm resistor.​

Answer 1

Given info : Two cells of emf 3V and 2V and internal resistance 1.5 ohm and 1 ohm respectively are connected in parallel so as to send current in the same direction through an external resistance of 3 ohm.

To find : The potential difference across 3 ohm is ...

solution : two cells are in parallel combination,

so equivalent resistance of their internal resistance, $r_{eq}=\frac{r_1r_2}{r_1+r_2}$

here, $r_1=1.5ohm ,r_2=1ohm$

so, $r_{eq}=\frac{1.5\times1}{1.5+1}=0.6ohm$

now equivalent emf of cells, $E_{eq}=\left[\frac{E_1}{r_1}+\frac{E_2}{r_2}\right]r_{eq}$

= [3/1.5 + 2/1] × 0.6

= [2 + 2] × 0.6

= 2.4V

now potential across 3 ohm resistor, $V=\frac{R}{R+r_{eq}}E_{eq}$

= 3/(3 + 0.6) × 2.4

= 3/3.6 × 2.4

= 2V

Therefore the potential across 3 ohm resistor is 2 Volts.

Answer 2

Answer:

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