Question

The total resistance in the parallel combination of three resistance $r_{2}$, and 5$\rho$ is

• A. $\frac{r_{1}}{r_{2}}\frac{\rho}{2}$
• B. $\frac{r_{2} - r_{1}}{r_{1}r_{2}}\frac{\rho}{4\pi}$
• C. $\frac{r_{1}r_{2}}{r_{2} - r_{1}}\frac{\rho}{4\pi}$
• D. $2\Omega,4\Omega$

Answer 1

Answer: (D)

$2\Omega,4\Omega$

Answer 2

: In the parallel combination of three resistances, the equivalent resistance is.,

$\frac{1}{R_{eq}} = \frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{3}}$

or, $\frac{1}{R_{eq}} = \frac{1}{9} + \frac{1}{7} + \frac{1}{5} = \frac{35 + 45 + 63}{315} = \frac{143}{315}$

$R_{eq} = \frac{315}{143} = 2.02\Omega$