JEE Main 2017 · 9 Apr · Shift 1 · Physics Q17

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PhysicsSingle correct+4 / -1Question 17 of 90

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 $P_1$ , $P_2$ and $P_3$ respectively, then :

Three networks of 1 Ω resistors, each across a 3 V battery. (I): five resistors forming a balanced bridge between the battery terminals. (II): a diamond of four resistors with a fifth joining its top and bottom, which are the battery terminals. (III): a diamond of four resistors (a balanced bridge with no middle link) in series with one more resistor.

P_1>P_2>P_3

P_1>P_3>P_2

P_2>P_1>P_3

P_3>P_2>P_1

Answer and worked solution

Official answer: C

(I): the five resistors form a balanced bridge, so the middle one carries no current and $R_1=1$ Ω.
(II): two 2 Ω paths and a 1 Ω link between the same nodes, so $R_2=2\parallel2\parallel1=0.5$ Ω.
(III): a balanced diamond (1 Ω) in series with 1 Ω, so $R_3=2$ Ω.

With $P=\frac{V^2}R$ , $P_2>P_1>P_3$ .

Topics:Wheatstone bridge and metre bridge Series and parallel resistors Electrical power and heating

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JEE Main 2017 · 9 Apr · Shift 1, Physics question 17