
The current in resistance $R _2$ would be zero if
$(A)$ $V_1=V_2$ and $R_1=R_2=R_3$
$(B)$ $V_1=V_2$ and $R_1=2 R_2=R_3$
$(C)$ $V_1=2 V_2$ and $2 R_1=2 R_2=R_3$
$(D)$ $2 V _1= V _2$ and $2 R _1= R _2= R _3$
$[1]$ battery emf is increased
$[2]$ all resistances are increased by $10\,ohms$
$[3]$ all resistances are made five times
$[4]$ the battery and the galvanometer are interchanged



