The total resistance in the parallel combination of three resistances 9 Ω, 7 Ω and 5 Ω is

Question

The total resistance in the parallel combination of three resistances 9 Ω, 7 Ω and 5 Ω is (A) 1.22 Ω (B) 2.29 Ω (C) 4.22 Ω (D) 2.20 Ω

Tardigrade Admin · Accepted Answer

In the parallel combination of three resistances, the equivalent resistance is (1/Req)=(1/R1)+(1/R2)+(1/R3) or (1/Req)=(1/9)+(1/7)+(1/5)=(143/315) ; Req=(315/143)=2.20 Ω

Q. The total resistance in the parallel combination of three resistances $9 Ω$ , $7 Ω$ and $5 Ω$ is

$1.22 Ω$

$2.29 Ω$

$4.22 Ω$

$2.20 Ω$

In the parallel combination of three resistances, the equivalent resistance is
$\frac{1}{R _{e q}} = \frac{1}{R _{1}} + \frac{1}{R _{2}} + \frac{1}{R _{3}}$
or $\frac{1}{R _{e q}} = \frac{1}{9} + \frac{1}{7} + \frac{1}{5} = \frac{143}{315}$ ;
$R_{e q} = \frac{315}{143} = 2.20 Ω$

Q. The total resistance in the parallel combination of three resistances 9Ω, 7Ω and 5Ω is

1.22Ω

2.29Ω

4.22Ω

2.20Ω