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NEET Physics: Kirchhoff's laws and bridges Practice Questions

13 free multiple-choice questions on Kirchhoff's laws and bridges (Current Electricity) for NEET Physics, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.

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  1. Q1. In a series circuit, if the total resistance increases, the total current flowing through the circuit will:

    • ABecome zero
    • BDecrease
    • CRemain the same
    • DIncrease
    Show answer & explanation

    Correct answer: B — Decrease

    According to Ohm's Law (I = V/R), if the voltage (V) remains constant, an increase in total resistance (R) will result in a decrease in the total current (I).

  2. Q2. A circuit consists of two batteries and three resistors. If we apply Kirchhoff's Voltage Law (KVL) to a closed loop, what principle does it govern?

    • AOhm's Law
    • BConservation of Charge
    • CKirchhoff's Current Law (KCL)
    • DConservation of Energy
    Show answer & explanation

    Correct answer: D — Conservation of Energy

    KVL is based on the principle of conservation of energy, stating that the algebraic sum of potential differences (voltage drops and rises) around any closed loop must be zero.

  3. Q3. If the currents entering a junction are 5A and 3A, and the current leaving is 8A, what is the net current entering that junction? (Using KCL)

    • A2A
    • B5A
    • C16A
    • D0A
    Show answer & explanation

    Correct answer: A — 2A

    KCL requires ΣIᵢₙ = ΣIₒᵤₜ. If 5A + 3A = 8A, then the net current entering is 8A - (5A + 3A) = 0A. If we consider only the flow into the junction, the balance equation is Iᵢₙ = Iₒᵤₜ, so Iᵢₙ = 8A. If the question asks for the net input current, it is the difference between input and output flow, or simply the total current flowing through the junction if input equals output. Assuming the standard KCL formulation: Input current = 8A.

  4. Q4. The Wheatstone bridge is a circuit used primarily to experimentally determine:

    • APower
    • BResistance
    • CCurrent
    • DPotential Difference
    Show answer & explanation

    Correct answer: B — Resistance

    The Wheatstone bridge is a circuit used to find an unknown resistance by balancing the bridge, which relies on the principle that the ratio of resistances is equal.

  5. Q5. In a simple series circuit containing three resistors R₁, R₂, and R₃, if the total equivalent resistance R₍eq) is 50 Ω, and R₁ and R₂ are in series with R₃, what is the relationship between the resistances?

    • AR₍eq) = R₁ R₂ R₃ / (R₁ + R₂ + R₃)
    • BR₍eq) = R₁/R₂ + R₃
    • CR₍eq) = R₁ || R₂ || R₃
    • DR₍eq) = R₁ + R₂ + R₃
    Show answer & explanation

    Correct answer: D — R₍eq) = R₁ + R₂ + R₃

    In a series circuit, the total equivalent resistance is the sum of the individual resistances. R₍eq) = R₁ + R₂ + R₃.

  6. Q6. Which law is used to determine the relationship between the voltages and currents in a closed loop circuit?

    • AKirchhoff's First Law
    • BOhm's Law
    • CKirchhoff's Current Law (KCL)
    • DKirchhoff's Second Law
    Show answer & explanation

    Correct answer: D — Kirchhoff's Second Law

    Kirchhoff's Second Law (KVL) states that the algebraic sum of the potential differences (voltage drops) around any closed loop in a circuit is zero.

  7. Q7. Which statement is fundamentally based on the principle of conservation of energy in an electrical circuit, as defined by Kirchhoff's Voltage Law (KVL)?

    • AThe current flowing through a resistor is inversely proportional to its resistance.
    • BThe algebraic sum of potential differences around any closed loop is zero.
    • CThe total resistance in the circuit is additive.
    • DThe total power dissipated in the circuit remains constant.
    Show answer & explanation

    Correct answer: B — The algebraic sum of potential differences around any closed loop is zero.

    Kirchhoff's Voltage Law (KVL) states that the algebraic sum of potential differences (voltage drops) around any closed loop in a circuit is zero, which is a direct application of the conservation of energy principle.

  8. Q8. A bridge circuit, governed by Kirchhoff's laws, requires the application of two independent equations (one for current, one for voltage) to solve for the unknown quantities in the network. What is the primary function of applying these laws?

    • ATo determine the direction of current flow.
    • BTo calculate the maximum power delivered by the source.
    • CTo find the total resistance of the circuit.
    • DTo ensure the conservation of energy and charge within the circuit.
    Show answer & explanation

    Correct answer: D — To ensure the conservation of energy and charge within the circuit.

    The primary function of applying Kirchhoff's laws in complex networks is to enforce the physical laws of conservation of charge (KCL) and energy (KVL) within the network.

  9. Q9. In a bridge circuit, if the condition for balance is not met, what does this imply about the current flow within the circuit?

    • AThe circuit is a short circuit
    • BThe total current is zero
    • CThe bridge is open
    • DThe balance condition fails, meaning the bridge is unbalanced and unequal currents flow through the paths
    Show answer & explanation

    Correct answer: D — The balance condition fails, meaning the bridge is unbalanced and unequal currents flow through the paths

    If the bridge is unbalanced (not in equilibrium), it implies that the currents flowing through the bridge arms are unequal, indicating that the bridge is unbalanced.

  10. Q10. Kirchhoff's Current Law (KCL) is a fundamental principle applied at which point in an electrical network?

    • AIn a closed loop
    • BAcross a single resistor
    • CAt any junction or node
    • DIn a series circuit
    Show answer & explanation

    Correct answer: C — At any junction or node

    KCL states that the algebraic sum of currents entering a junction must equal the sum of currents leaving that junction. This is applied at junctions (nodes).

  11. Q11. In a series circuit, the total resistance is calculated by:

    • AR_total = 1/R1 + 1/R2 + 1/R3
    • BR_total = R1 / (R2 + R3)
    • CR_total = R1 * R2 * R3
    • DR_total = R1 + R2 + R3
    Show answer & explanation

    Correct answer: D — R_total = R1 + R2 + R3

    In a series circuit, resistances add up linearly. R_total = R1 + R2 + R3.

  12. Q12. If three currents enter a junction point, the algebraic sum of these currents must be zero according to KCL. What does this imply about the flow of charge?

    • ACharge is created at the junction.
    • BThe currents must all be equal to zero.
    • CCharge is destroyed at the junction.
    • DCharge is conserved, meaning the total charge entering equals the total charge leaving.
    Show answer & explanation

    Correct answer: D — Charge is conserved, meaning the total charge entering equals the total charge leaving.

    KCL implies the conservation of charge. If currents enter and leave a junction, the total charge must be conserved, meaning the sum of currents entering must equal the sum of currents leaving.

  13. Q13. Kirchhoff's Current Law (KCL) is based on the principle of conservation of which physical quantity?

    • AMomentum
    • BEnergy
    • CMass
    • DCharge
    Show answer & explanation

    Correct answer: D — Charge

    Kirchhoff's Current Law states that the algebraic sum of currents entering a junction must equal the sum of currents leaving it. This is a direct consequence of the conservation of electric charge.

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