Electricity & Magnetism · GCSE Physics Topic 4 (Electricity)
Series-Parallel Circuit Fault & Rheostat Simulator
Key exam takeaway: A voltmeter reading near supply voltage indicates an open circuit across its terminals. A zero reading indicates either a short across it or an open outside.
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Parameter Controls
V
Ω
Ω
Live Derivations & Metrics
Ammeter Current I
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R1 Voltmeter U1
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R2 Voltage U2
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Circuit Health Status
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Real-Time Formula Derivation
Governing Formula:
--Substitution:
--Regime: --
Related Tool:
⚡ Standard Tool: Ohm's Law Calculator ↗
Worked Examples & Exam Question Deep Dive
Worked Problem
Problem: In series circuit (E=6V, R1=10Ω, R2), ammeter reads 0A while voltmeter across R1 reads 6V. Diagnose the fault.
Step-by-Step Derivation:
- R1 has an open circuit! Zero current means an open branch; voltmeter reading 6V proves the rest of the circuit is intact and R1 is severed.
Worked Problem
Problem: A rheostat reads "50Ω 1.5A". What do these mean? Why connect "one top, one bottom" terminal?
Step-by-Step Derivation:
- "50Ω" is maximum resistance, "1.5A" is maximum continuous safe current. "One top one bottom" ensures variable resistance path.
Student Inquiry Worksheet & Practice Problems
Q1. Variant 1: Where should the rheostat slider be positioned before closing the circuit switch? Why?
Answer Key: At maximum resistance (furthest from active bottom terminal) to minimize initial inrush current, protecting meters and bulbs.
Q2. Variant 2: What is the "series-reverse, parallel-same" dynamic circuit heuristic?
Answer Key: When variable resistance R increases: voltage and current across series components decrease ("series-reverse"); across parallel branches they increase ("parallel-same").
Q3. Variant 3: In a parallel circuit, if one branch opens, do others fail? Why are home appliances wired in parallel?
Answer Key: Unchanged! Parallel branches receive independent line voltage. Home parallel wiring guarantees independent operation when any one switch is toggled.
Frequently Asked Questions & Misconceptions
Can a voltmeter be connected directly across a battery? What about an ammeter?
Voltmeter: YES (huge internal resistance draws negligible current). Ammeter: STRICTLY FORBIDDEN (near-zero resistance causes dead short, burning the meter).
Why does a bulb turn off when short-circuited?
A short places zero-resistance wire across the bulb; virtually all current bypasses through the wire, depriving the bulb of voltage and power.
What are the two common triggers for residential circuit breaker trips?
1) Short circuit (hot and neutral touch directly, infinite current trip); 2) electrical overload (excessive appliances run simultaneously, I = P/U exceeds rated trip current).
In a series circuit, does a larger resistor take more or less voltage?
More voltage! Current is uniform (I1=I2). By U = IR, voltage divides in direct proportion to resistance (U1/U2 = R1/R2).