Let there be n resistors R1……..Rn with Rmax = max(R1……Rn)

Question:

Let there be n resistors R1……..Rn with Rmax = max(R1……Rn) and Rmin = min(R1…….Rn). Show that when they are connected in parallel, the resultant resistance Rp < Rmin and when they are connected in series, the resultant resistance Rs > Rmax. Interpret the result physically.

Solution:

Following is the parallel grouping of the resistance:

Rp = 1/R1 + 1/R2 + …. + 1/Rn

Rmin/Rp = Rmin/R1 + Rmin/R2 + …..+Rmin/Rn

The RHS is equal to 1

Therefore, Rp < Rmin

Following is the series grouping of the resistance:

Rs = R1 + R2 + …… + Rn

Rs = R1 + ….. +Rmax+…..+Rn

Rs = Rmax(R1+……..Rn)

Therefore, series combination has an equivalent resistance of resistors which is greater than the maximum resistance in parallel combination.

Physical interpretation is:

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