JEE Main 2025 Jan 23 Shift 1, Physics Q15: Kirchhoff’s Laws

JEE Main2025Jan 23, Shift 1Physics

Refer to the circuit diagram given in the figure, which of the following observation are correct?

A. Total resistance of circuit is 6 $Ω$ .

B. Current in Ammeter is 1 A

C. Potential across AB is 4 Volts.

D. Potential across CD is 4 Volts.

E. Total resistance of the circuit is 8 $Ω$ .

Choose the correct answer from the options given below:

A
A, B and D only
B
A, C and D only
C
B, C and E only
D
A, B and C only

Solution

The diode is forward biased in this layout, so it acts like a wire. Redraw the network: the 4 $Ω$ from D-down and the 4 $Ω$ from A-down are in parallel ( $= 2 Ω$ ). This combination is in series with the 4 $Ω$ between C and D, giving $4 + 2 = 6 Ω$ for that branch. With nothing else in series, $R_{net} = 6 Ω$ (A ✓; E ✗).

Current from the battery: $I = \frac{6 V}{6 Ω} = 1$ A through the ammeter (B ✓).

This current splits equally (0.5 A each) at D between the two parallel 4 $Ω$ resistors. Potential across AB (the 4 $Ω$ from A to B) carries 0.5 A: $V_{A B} = 0.5 \times 4 = 2$ V (C ✗).

Potential across CD (the 4 $Ω$ between C and D) carries the full 1 A: $V_{C D} = 1 \times 4 = 4$ V (D ✓).

$∴$ A, B, and D only.

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JEE Main 2025 Jan 23 Shift 1, Physics Q15: Kirchhoff’s Laws

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