Question

A battery of internal resistance $4\Omega$ is connected to the network of resistances as shown. In order to give the maximum power to the network, the value of R (in $\Omega$) should be

• A. $\frac{4}{9}$
• B. $\frac{8}{9}$
• C. 2
• D. 18

Answer 1

The correct option is C 2

The equivalent circuit becomes a balanced wheatstone bridge


For maximum power transfer, external resistance should be equal to internal resistance of source
$\Rightarrow \frac{(R+2R)(2R+4R)}{(R+2R)+(2R+4R)}=4$ i.e. $\frac{3R\times 6R}{3R+6R}=4$ or $R=2\Omega$