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Current Electricity — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsCurrent Electricity3 Marks
Question
The graph shown here shows the variation of terminal potential difference V, across a combination of three cells in series to a resistor, versus current i:
  1. Calculate the emf of each cell.
  2. For what current i, will the power dissipation of the circuit be maximum?
✓

Answer

Let $\varepsilon$ be emf and r the internal resistance of each cell. The equation of terminal potential difference.
V = $\varepsilon$ eff - i rint becomes,
V = $3\varepsilon$ -i rint …(i)
Where rint is effective (total) internal resistance.
From fig., when i = 0, V = 6.0V
$\therefore$ From (i), $6=3\varepsilon-0\Rightarrow\varepsilon=\frac63=2\text{V}$
i.e., emf of each cell, $\varepsilon=2\text{V}$
Thus, emf of each cell, $\varepsilon=\text{2V}.$

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