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The current in the given circuit is

Asked in CBSE AIPMT 1999 · Series and parallel combinations

Figure: Series and parallel combinations

(1) 4.9 A
(2) 6.8 A
(3) 8.3 A
(4) 2.0 A

Answer: (4) 2.0 A

Step-by-step solution

The cell joins the top vertex and the bottom-left vertex of the triangle.

Between those two vertices: R_A=3 Ω directly, in parallel with R_B+R_C=6+6=12 Ω.

R_eq=(3×12)/(3+12)=2.4 Ω.

I=(4.8)/(2.4)=2.0 A.

Why the other options are wrong

(1) No single slip gives this value; 4.9 A needs a total resistance under 1 Ω, smaller than even all three resistors in parallel (1.5 Ω).
(2) No single slip gives this value; 6.8 A needs about 0.7 Ω, smaller than even all three resistors in parallel (1.5 Ω).
(3) No single slip gives this value; 8.3 A needs about 0.6 Ω, smaller than even all three resistors in parallel (1.5 Ω).

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