(455) Circuit analogy 2 (resistors, series and parallel) [IB Physics SL/HL]

Voltmeters and Ammeters

• Voltmeter: Measures electric potential difference, represented by chocolate in the analogy (1 volt = 1 piece of chocolate). In circuits, connected in parallel.

• Ammeter: Measures current, connected in series within the circuit.

Resistors and the Chocolate Analogy

• Chairs: Represent resistors. Crossing a chair costs chocolate, indicating potential loss (similar to how resistors lower electric potential).

• Resistance: Measured in ohms (Ω), denoted as R. Represents the height of the chair in the analogy.

• Total Resistance in Series: Add up all resistors (R_total = R1 + R2 + ...).

  • Example: With equal resistors (chairs), potential loss is divided equally among them.

• Potential Distribution: If V_total is 1V, then V1 (from first resistor) + V2 (from second resistor) = 1V.

Current in Series Circuits

• Current remains constant throughout; total current (I_total) equals current through each resistor (I1 + I2 + ...).

Parallel Circuits

• Equivalent Resistance in Parallel: Calculated using 1/R_total = 1/R1 + 1/R2 + ...

• In parallel circuits, potential difference across each resistor remains the same (V1 = V2 = ...).

  • Total potential equates to V_total; each path chosen by charge (coulombs) consumes the same amount of potential (1 volt).

• Current in Parallel Circuits: Divided among paths. Sum of currents entering a junction equals sum of currents leaving (I_total = I1 + I2).

  • Current distribution varies based on resistor values but adds up accordingly.