Question

When some potential difference is maintained between $A$ and $B$, current $I$ enters the network at $A$ and leaves at $B$

• A. the equivalent resistance between $A$ and $B$ is $8\Omega$
• B. $C$ and $D$ are at the same potential
• C. no current flows between $C$ and $D$
• D. current $\frac{31}{5}$ flows from $D$ to $C$

Answer 1

Answer: (A), (B), (D)

The correct options are
A the equivalent resistance between $A$ and $B$ is $8\Omega$
B $C$ and $D$ are at the same potential
D current $\frac{31}{5}$ flows from $D$ to $C$

From the figure,

As $C$ and $D$ are joined, they must be at the same potential, and may be treated as the same point. This gives the equivalent resistance as $8\Omega$.

If we distributed current in the network, using symmetry.
$V_A-V_D=V_A-V_C$

or $20i=5(I-i)$

or $i=I/5$

$I-2i=I-\frac{2I}{5}=\frac{3I}{5}=$ current flowing from $D$ to $C$.