Question

a fixed resistance r1 and a variable resistance r2 are connected in parallel. If the value of r2 can be varied between zero and infinity,what is the minimum and maximum possible resistance of the parallel combination?​

Answer 1

Answer:

Resistance will vary from 0 to r1

Explanation:

A fixed resistance r1 and a variable resistance r2, are connected in parallel. If the value of r2 can be varied between zero and infinity, what is the minimum and maximum possible resistance of the parallel combination ? (A) 0, INFINITY (B) r1, r1+r2 (C) 0, r1 (D) r2, r1+r2​

1/R  = 1/r1 + 1/r2

When r2 = ∞

=> 1/R = 1/r1  + 0

=> R = r1

1/R = 1/r1 + 1/r2

=> 1/R = (r1 + r2)/r1r2

=> R = r1r2/(r1 + r2)

when r2 = 0

=> R = 0

=> Resistance will vary from 0 to r1