Question

In Wheatstone's bridge P = 7 ohm, Q = 12 ohm, R = 3 ohm and S = 8 ohm. How much resistance must be put in parallel to the resistance S to balance the bridge?

Options

• 24 ohm

• 14.4 ohm

• 19.5 ohm

• 5.14 ohm

Answer 1

14.4 ohm

Explanation:

`"For balancing the bridge"  "P"/"Q" = "R"/"S'"`

`therefore "S'" = ("R" xx "Q")/"P" = (3 xx 12)/7 = 36/7`

`therefore  1/"S'" = 1/"r" + 1/8`

`therefore  7/36-1/8=1/"r"`

`therefore "r" = 72/5 = 14.4  Omega`