Question

A parallel combination of three resistors takes 7.5A from a supply of 30V. it two resistors are 10ohm and 12ohm,find the third resistor.​

Answer 1

Answer:

ITotal = 7.5A

V = 30V

(V/I) = {(30)/(7.5)} = 4

i.e. RTotal = 4Ω

Let third resistor be R.

hence (1/4) = (1/10) + (1/12) + (1/R)

∴ (1/R) = (1/4) – (1/10) – (1/12)

∴ (1/R) = {(15 – 6 – 5)/(60)}

∴ (1/R) = (4/60) = (1/15)

R = 15Ω

Answer 2

Answer:

The correct option (B) 15Ω

Explanation:

Total = 7.5A V = 30V (V/I) = {(30)/(7.5)} = 4 i.e. RTotal = 4Ω Let third resistor be R. hence (1/4) = (1/10) + (1/12) + (1/R) ∴ (1/R) = (1/4) – (1/10) – (1/12) ∴ (1/R) = {(15 – 6 – 5)/(60)} ∴ (1/R) = (4/60) = (1/15) R = 15Ω