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The value of current I in the electrical circuit as given below, when potential at A is equal to the potential at B, will be ______ A. [Figure: between left node L and right node N, a top branch 10 Ω to node A then 20 Ω to N, and a bottom branch R to node B then 40 Ω to N; 30 Ω between A and B. A 40 V cell and key K connected between L and N; current I enters at L and leaves at N.]

Asked in JEE Main 28th Jan 2nd Shift 2025 · Wheatstone bridge

Figure: Wheatstone bridge
Answer: 2

Step-by-step solution

V_A=V_B means the bridge is balanced: (10)/(20)=R/(40), so R=20 Ω.

The 30 Ω carries no current.

R_eq=(10+20)∥(20+40)=(30×60)/(90)=20 Ω.

I=(40)/(20)=2 A.

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