Node law — current conservation: At a junction (node) in an electrical network, is it possible for the total current entering the node to differ from the total current leaving the node under normal steady conditions?
Correct Answer: Incorrect
Introduction / Context:Kirchhoff’s Current Law (KCL) states that the algebraic sum of currents entering and leaving a node is zero. This embodies conservation of charge and is fundamental to circuit analysis across DC and AC regimes for lumped networks.
Given Data / Assumptions:
- Ideal lumped-element circuit model.
- Steady conditions or sinusoidal steady state for AC.
- No charge accumulation at an ideal node.
Concept / Approach:KCL arises because charge cannot pile up indefinitely at a point in a lumped model; any current arriving must depart. Mathematically, sum(I_in) = sum(I_out). Transient elements like capacitors are handled by defining branch currents consistently; KCL still holds at every instant when displacement currents are included in Maxwell-consistent models.
Step-by-Step Solution:
1) Define the node and enumerate incident branch currents with a sign convention. 2) Apply conservation of charge: net inflow equals net outflow. 3) Conclude that entering current cannot differ from leaving current in the model. 4) Use KCL to solve for unknown currents in parallel networks.Verification / Alternative check:Simulations and nodal analysis rely on KCL; measured discrepancies typically result from instrument error or parasitic storage, not a violation of the law itself within the lumped model assumptions.
Why Other Options Are Wrong:
- Correct: The statement is not correct; KCL forbids a mismatch.
- True only during capacitor charging: KCL still holds when capacitor branch current is included.
- True only at very high frequency: KCL holds; modeling may require displacement current but conservation remains.
- True if the meter accuracy is low: Measurement error does not change physical laws.
Common Pitfalls:Interpreting meter mismatch as a physical violation; overlooking displacement currents in high-frequency or field-theory contexts and then misapplying the lumped model.
Final Answer:Incorrect