Question

Two identical slabs of given metal are joined together in two different ways as shown in figure. What is the ratio of the resistance of these two combinations?

Answer 1

Let `l` and A be the length and area of cross-section of the each of the two slabs. Then `R= rho l//A`
`R_(1) = (rho 2l)/A = 2R`
`R_(2) = (rho l)/(2A)= R/2`
`R_(1)/R_(2)=(2R)/(R//2) = 4 or R_(1) : R_(2)=4:1`