🔍 Key Concepts

• How resistances combine in series circuits versus parallel circuits • Identifying the actual current path in figure B when the switch is closed • Formula for total resistance in series: the resistances are added directly

💭 Think About

• Trace the path from the positive side of the source Es, through the fuse and switch, past R1, R2, and R3, and back to the negative side. Do you ever have a point where current can split into two paths? • If the current has only one possible path, how do you combine the resistor values to find the total effective resistance? • Compare the total you calculate to the answer choices—does it look more like the result of adding, or of a parallel combination?

✅ Before You Answer

• Confirm that all three resistors (R1, R2, R3) are in the same single loop with no branching junctions • Use the correct formula: for series circuits, (R_T = R_1 + R_2 + R_3); for parallel, (1/R_T = 1/R_1 + 1/R_2 + 1/R_3) • Double‑check each resistor value (3 Ω, 4 Ω, 5 Ω) is included once in your calculation before matching to the closest answer choice