Why when I reverse one of the three batteries in a torch light, the bulb does not light up? The three batteries (one of them is reversed) and the bulb suppose to form a closed loop. According to Kirchhoff's 2nd law,
$IR = E_1 + E_2 - E_3$
If all the batteries are identical ($1.5$ V for example), then IR$ = 1.5$V. That means there is still an electric current flows through the bulb. Is there any reason why the bulb does not light up?