Concept:This is a balanced Wheatstone bridge, so the middle branch carries no current.
Explanation:For the bridge to be balanced, the ratio of resistances in opposite arms must be equal.
Here,
RBCRAB=1010=1and
RDCRAD=3030=1.
Since both ratios are equal, the bridge is balanced and no current flows through branch
BD.
The circuit then simplifies to two parallel branches between
A and
C.
Upper branch resistance:
R1=10+10=20 ΩLower branch resistance:
R2=30+30=60 ΩEquivalent resistance is given by:
Req1=R11+R21Req1=201+601=603+1=604Req=15 ΩUsing Ohm's law with battery voltage
V=3 V:
I=ReqV=153=0.2 AAnswer:The current drawn from the battery is
0.2 A (Option C).