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Question:

The figure shows three circuits I, II and III which are connected to a 3V battery. If the powers dissipated by the configurations I, II and III are P1, P2 and P3 respectively, then :

P3>P2>P1

P1>P3>P2

P2>P1>P3

P1>P2>P3

Solution:

The correct option is B
P2>P1>P3
It is a wheatstone bridge and current through 2-3 will be zero.Equivalent resistance=2R∥2R⇒Req=R⇒P1=V²/R
For (II)⇒Req=2R∥R∥2R⇒Req=2R.R.2R/(2R²+2R²+4R²)⇒Req=R²/2⇒P2=2V²/R
For (III)⇒Req=2R∥(2R+R)=2R⇒P3=V²/2R
P2>P1>P3