Effective resistance between A and B in the following circuit

Options

A. `10Omega`
B. `20Omega`
C. `5Omega`
D. `20//3Omega`

Answer

A

Explanation

Circuit canbe redrawn as

`R_(1)andR_(2)` are resistances given at left most top edges of the diagram in question.
Figure (1) resembles a circuit of Wheat Stone Bridge in which battery and central branch resistance are interchanged and circuit satisfies

`(P)/(Q)=(R)/(S)`
Since the adjacent diagram satisfies `(P)/(Q)=(R)/(S)`,
no current flow through `R_(1)andR_(2)`.
We go back to original diagram figure (1).
If we connect battery between A and B.
no current flows through `R_(1)andR_(2)`.
`R_(eff)=(10Omega+10Omega||(10Omega+10Omega)=10Omega`