Question

How can I get answer of Q.6
help please

Answer 1

Hi friend,

Potential difference across points B and D will be zero when given arrangements of resistances form a wheatsone bridge.
R₁/R₂=R₃/R₄ 
R₁=12+4=16Ω
R₂=3+1=4Ω
R₃=xΩ
R₄=1/2Ω
So, 16/4=x/0.5
       4(0.5)=x
       2Ω=x
Therefore x=2Ω for which potential difference across B and D will be zero.
HOPE THIS HELPS..............

Answer 2

(Potential difference across given points B and D will be 0 when the arrangement forms wheatstone bridge.
Therefore,
R1/R2 = R3/R4 , R1 = (12+14) Ω , R2 = (3+1)Ω , R3 = XΩ , R4 = 1/2 Ω

or,16/4 = x/1/2
or, 4 = 2x
or, x = 4/2
Or, x = 2Ω.

answer) potential difference across B and D will be zero for x = 2 Ω