If c/d is in inverse ratio to a/b, then a/b = d/c (see Exercises 29 and 30). The current i (in A) in an electric circuit is in inverse ratio to the resistance R (inΩ). If i = 0.25 mA when R = 2.8Ω, what is i when R = 7.2 Ω?

Data from Exercises 29

In an electric instrument called a “Wheatstone bridge,” electric resistances are related by

R₁=  6.00 Ω
R₃ =  62.5 Ω,  and
R₄ = 15.0 Ω.  
See Fig. 18.4.

R R R R