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MCQEasyJEE 2025Kirchhoff's Laws & Circuits

JEE Physics 2025 Question with Solution

What is the current through the battery in the circuit shown below?

Circuit with a 5 V battery connected to two parallel branches, each branch containing a diode in series with a 20 ohm resistor, both diodes oriented in the same direction.
  • A

    1.0 A1.0 \, \text{A}

  • B

    1.5 A1.5 \, \text{A}

  • C

    0.5 A0.5 \, \text{A}

  • D

    0.25 A0.25 \, \text{A}

Answer

Correct answer:C

Step-by-step solution

Standard Method

Given: A 5 V5 \, \text{V} battery is connected to two branches, each having a diode in series with a 20 Ω20 \, \Omega resistor.

Find: The current through the battery.

The solution states that the current through the battery is obtained using circuit analysis and Ohm's law:

I=VRtotalI = \frac{V}{R_{\text{total}}}

It further concludes that the calculated current is 0.5 A0.5 \, \text{A}.

Therefore, the correct option is C.

Extracted Hint-Based Method

Given: Determine the current through the battery by first finding the equivalent resistance of the circuit.

Find: Battery current.

The extracted hint says to determine the total resistance using series and parallel combinations, and then apply Ohm's law:

I=VRI = \frac{V}{R}

The extracted solution text does not provide complete intermediate resistance calculations from the diagram, but it explicitly identifies the final current as 0.5 A0.5 \, \text{A}.

Hence, the current through the battery is 0.5 A0.5 \, \text{A}, so the correct option is C.

Common mistakes

  • Assuming the current can be found without first identifying the effective resistance. This is incorrect because Ohm's law requires the net resistance seen by the battery. First reduce the circuit properly, then use I=VRI = \frac{V}{R}.

  • Adding branch resistances blindly as series resistors. This is wrong because different branches may form a parallel combination depending on the conducting path. Check the circuit topology before combining resistors.

  • Ignoring the role of the diodes. This is incorrect because diode orientation determines whether a branch conducts or blocks current. Always inspect the diode direction before calculating equivalent resistance.

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