Question

Five resistors are connected as shown in adjoining figure.
The effective resistance i.e., equivalent resistance between the points $A$ and $B$ is

• A. $4\Omega$
• B. $5\Omega$
• C. $15\Omega$
• D. $20\Omega$

Answer 1

Answer: (A)

$4\Omega$

This combination of resistors follows the concept of Wheatstone Bridge.

When the ratio of the resistors (excluding the middle one) are equal i.e. $\frac{R_1}{R_2}=\frac{R_3}{R_4}$, then the current through the bridging resistor is zero.

As we can see $\frac{2}{3}=\frac{8}{12}$.

Hence, the net resistance will be $R=4$.