Question

please help me in solving this question please don't use the expression given in book I. e. the last line
please solve on a paper and explain the error in resistance in parallel...please help now tomorrow is my physics exam!! ​

Answer 1

Answer:

a) R' = R1 + R2       for resistors in series

    R' = 100 + 200 = 300 ohms

b) 1 / R' = 1 / R1 + 1 / R2  or     R' = R1 * R2 / (R1 + R2)    for parallel resistors

   R' = 100 * 200 / (100 + 200) = 66.7   ohms

c) dR' / R'^2 = dR1 / R1^2 + dR2 / R2^2    represents the fractional uncertainty of the parallel combination

You are given +- 3 ohms for R1 and +- 4 ohms for R2

dR1 / R1^2 = 3 / 10000 = .0003

dR2 / R2^2 = 4 / 40000 = .0001

So dR' / R'^2 = .0004

dR' = .0004 * (66.7)^2  = 1.78 ohm for the uncertainty of the parallel combination