Current Electricity and Electrical InstrumentHard
Question
The effective resistance between points P and Q of the electrical circuit shown in the figure is


Options
A.

B.

C.2r + 4R
D.
+ 2r
+ 2rSolution
The circuit is symmetrical about axis POQ. Therefore the equivalent circuit is drawn

⇒ RPQ =
If a poential difference is applied across P and Q, there will be no currents in arms AO and OB. So these resistance will be ineffective
⇒ RPQ =

If a poential difference is applied across P and Q, there will be no currents in arms AO and OB. So these resistance will be ineffective
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