In figure (a), the resistors are connected in parallel between X and Y.

Let R’ be the resistance they have in common.

1 / R’ now equals 1 / 2 + 1 / 2

= 2 / 2 ohm ohm ohm ohm ohm o

[1] R’ = 1 ohm

In figure, a series of two 1 ohm resistors is connected in parallel with another series of two 1 ohm resistors (d)

Two 1 ohm resistors in series resistance

R = (1 + 1) ohm

R = 2 ohm

As a result, we may say that 2 ohm resistors are paralleled across X and Y.

R’ denotes the total resistance across X and Y.

1 / R’ = 1 / 2 + 1 / 2 is the result.

1 / R’ = 2 / 2 ohm ohm ohm ohm ohm ohm oh

[2] R’ = 1 ohm

The figures (a) and (d) have the same equivalent resistance between X and Y, as shown by equations [1] and [2].