Question

If the resistance of a circuit having 12V source is increased by $4\Omega$, the current drops by 0.5A. What is the original resistance of circuit

• A. $4\Omega$
• B. $8\Omega$
• C. $16\Omega$
• D. $\frac{1}{16}\Omega$

Answer 1

The correct option is B $8\Omega$

let Resistance is

$V=I{R}_1$

So, $I=\frac{V}{R_1}$

In second case

$R_2=R_1+4$

$I_2=\frac{V}{R_1+4}$ = $I_1-0.5$

$\frac{12}{R_1+4}=I_1-0.5$

$R_1^2+4R_1^2-96=0$

$R_1^2+12R_1^2-8R_1^2-96=0$

$R_1=8\Omega$