Diagnosing a parallel circuit: A sudden increase in the total input current to a parallel network most likely indicates which change?
Correct Answer: an increase in source voltage
Introduction / Context:Troubleshooting parallel circuits requires understanding how source voltage and branch resistances affect total current. This item tests your qualitative reasoning about circuit behavior without heavy computation.
Given Data / Assumptions:
- Total current into a parallel network increases suddenly.
- No explicit component values are provided.
- Assume conventional resistive branches and steady-state conditions.
Concept / Approach:In a parallel circuit, I_total = V_source / R_eq. Therefore, an increase in I_total can be caused by either higher V_source or lower R_eq (e.g., a shorted branch). Conversely, opening a branch increases R_eq and reduces I_total; lowering V_source also reduces I_total.
Step-by-Step Reasoning:
Identify relation: I_total proportional to V_source and inversely proportional to R_eq.Evaluate options: a drop in source voltage → lowers current, not raises it.An open resistor (one branch removed) → fewer paths, higher R_eq → lower current.Only an increase in source voltage directly explains a sudden increase in total current (assuming no new short path is specified).Verification / Alternative check:If a shorted branch were present (not an answer choice), R_eq would fall dramatically and current would rise as well; however, among the given choices, the correct driver is higher source voltage.
Why Other Options Are Wrong:
- A drop in source voltage: Would reduce current.
- An open resistor: Raises R_eq and reduces current.
- Either of those: Both predict a decrease, not an increase.
Common Pitfalls:
- Confusing series and parallel behavior with component failures.
Final Answer:an increase in source voltage