Question

Two resistances of 1Ω and 2Ω are connected in series and then in parallel. Then the ratio of effective resistance of series and parallel combination of resistances is (1) (a) 2:9 (b)9:2 (c) 1:3 (d) 1:2

Answer 1

Answer:

option (b) 9:2

Explanation:

Let Total resistance in series=  Rs

Let total resistance in  parallel= Rp.

given R1=1 ohm and R2=2ohm.

therefore, Rs= 1 ohm +2 ohm=3 ohm.   since(Rs=R1+R2)

    and 1/Rp=1/1+1/2     since(1/Rp=1/R1+1/R2)

         = 1/Rp=2+1/2

         = 1/Rp=3/2 ohm.

    then Rp=2/3 (reciprocal).

   Ratio= Rs/Rp

therefore, Ratio = 3/2/3.

                          =9/2

                           =9:2

therefore, your answer will be option (b)

Hope it helps you:)

Answer 2

Answer:

it's different

Explanation:

from from Chinese maths