Which of the four resistances P,Q,R and S generate the greatest amount of heat when a current flows from A to B ?

$R_1=P+Q=2\Omega +4\Omega =6\Omega$

$R_2=R+S=1\Omega +2\Omega =3\Omega$

$I_1{R}_1=I_2{R}_2$

$I_1=\frac{R_2}{R_1}{I}_2=\frac{3}{6}{I}_2-\frac{I_2}{2}$

$\text{⇒}{I}_2=2I_1$

$\text{ Heat flow }H=I^{2}Rt$

$\text{ For }Q,H_Q=I_1^{2}Qt=\frac{I_2^2}{4}\times 4t=I_2^{2}t$

$\text{ For }S,H_S=I_2^{2}St=I_2^2·2t=2I_2^{2}t$

$\therefore \text{ Greatest amount of heat generated by }S$