Question

Two resistors when connected together can produce 25 ohm and in parallel 4ohm. Find value of each resistance.​

Answer 1

Answer:

The equivalent resistance is maximum if the resistances are connected in the series. Let's the resistance value is R1 and R2.

Explanation:

R1+R2 =25 ———-(1)

The equivent resistance value will be minimum if connected in the parallel.

R1R2/(R1+R2) =6

R1R2/25=6

R1R2= 25 x 6 =150

R1 R2=150

(R1-R2)^2={R1+R2) ^2–4R1R2

(R1-R2)^2=25 ^2–4*150

(R1-R2)^2=625–600

(R1-R2)^2=25

(R1-R2)=5

R1= R2+5 ———(2)

Putting value of R1 of eq(2) in eq(1)

R1+R2= 25

R2+5+R2= 25

2R2=25–5

R2=20/2

R2= 10 Ohms

R1= 15 Ohms

Answer 2

let first resistor is R1, and 2nd is R2, then in series combination , 25=R1+R2---->(1), in parallel combination , 4=R1×R2/R1+R2-----(2) then 4=R1×R2/25 from 1,2 equation , 100=R1×R2 So R1=20,R2=5 ohm