Question

21. Two resistances when connected in series their
resultant resistance is 10 ohm. but when they
are connected in parallel their resultant resistance
is 2.4 ohm. Find the values of each resistance
separately.​

Answer 1

Explanation:

When connected in series,

R 1 +R 2=9

R 2 =9−R 1

When connected in parellet,

1/R1+1/R2=1/2

1/R1+1/9-R1=1/2

9-R1+R2. =1/2R1(9-R1).

9/R1-R1² =1/2

R1²−9R 1 +18=0

(R 1 −3)(R 1 −6)=0

R 1 =3,6

So,

When R 1 =3Ω,R 2 =9−3=6Ω

When R 1 =6Ω,R 2=9−6=3Ω