Question

Two resistance wires on joining in parallel the resultant resistance is $\frac{6}{5}$ ohm. One of the wire breaks, the effective resistance is 2 ohm. The resistance of the broken wire was :-

• A. $\frac{3}{5}$
• B. 2 ohm
• C. $\frac{6}{5}$
• D. 3 ohm

Answer 1

The correct option is D 3 ohm

$\text{Step 1: Draw combination of resistances}$ $\text{[Ref. Fig. 1]}$

When $R_1$ is broken so effective resistance equal to $R_2=2\Omega$

$\text{Step 2: Calculation of find}{R}_1$ $\text{[Ref. Fig. 2]}$

$R_{eqparallel}=\frac{R_1\times 2}{R_1+2}$

$\Rightarrow \frac{6}{5}=\frac{R_1\times 2}{R_1+2}$

$\Rightarrow 6R_1+12=10R_1$

$R_1=3\Omega$

Option D is correct