Question

In your circuit toolbox you only have a collection of resistors (R1 = 100 ?, R2 = 15 ?, R3 = 60 ?), and some switches that can be open or closed. Construct a circuit below filling in all four boxes, such that the equivalent resistance between A and B is 20 ?.

in your circuit toolbox you only have a collection of resistors (R1 = 100 Ω , R2 = 15 Ω , R3-60 Ω ), and some switches that can be open or closed. Construct a circuit below filling in all four boxes, such that the equivalent resistance between A and B is 20 Ω R2

Answer 1

answer is as follows

let us number the boxes as a,b,c,d

in upper row let first box is 'a' and second box is 'b'

in lower row let first box is 'c' and second box is 'd'

now put resistance of 15 ohms in the box 'a' and 'b'

and put resistance of 60 ohms in box 'c' and put a short circuit in box 'd'

therefore resistance of upper row = 15 + 15 = 30 ohms

and resistance in lower row = 60 ohms

taking parallel combination ouput between point A and B

we get equivalent resistance between A and B is 20 Ω.