Question

A cell of emf $1.5V$ having a finite internal resistance is connected to a load resistance of $2\Omega$. For maximum power transfer, the internal resistance of the cell should be

• A. $4\Omega$
• B. $0.5\Omega$
• C. $2\Omega$
• D. None of these

Answer 1

The correct option is C $2\Omega$


Given, $R_l=2\Omega$
total current ($i$)=$\frac{1.5}{2+r}$
$P_{max}=i^{2}R$
$P_{max}=\frac{2\times {1.5}^2}{(r+2{)}^2}$
Using maximum power transformation theorem, in a circuit a maximum power flows when internal resistance will be equals to load resistance.
Hence, $r=R=2\Omega$

So, option C is correct.