Elektrizität & Magnetismus · AP Physics 2
Messbereichserweiterung & Innenwiderstand
Messbereichserweiterung für Drehspulmesswerke: Shunt-Widerstand und Vorwiderstand
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3D-Simulationsfenster● 60 FPS
Experimentelle Steuerungsparameter
μA
Ω
Echtzeit-Herleitung & Kennzahlen
Benötigter Widerstand R
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Widerstand des umgebauten Messgeräts
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Messbereichsfaktor n
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Schaltungstopologie
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Echtzeit-Formelherleitung
Grundformel:
--Einsetzungsschritte:
--Physikalischer Zustand: --
Typische Beispielaufgaben & Prüfungsfallen
Worked Problem
Aufgabe: A galvanometer has Ig=3mA and Rg=100Ω. Convert it to a 3V voltmeter. Find connection and resistance.
Schrittweise Herleitung:
- Series connection. Ug = 3mA*100Ω = 0.3V. Resistor must drop 2.7V. R = 2.7V / 3mA = 900Ω. Total internal resistance = 1000Ω.
Worked Problem
Aufgabe: Convert the same galvanometer (Ig=3mA, Rg=100Ω) into a 0.6A ammeter. Find connection and resistance.
Schrittweise Herleitung:
- Parallel connection. Shunt current I_s = 0.6 - 0.003 = 0.597A. Parallel voltage = 0.3V. Shunt resistance R = 0.3 / 0.597 ≈ 0.503Ω.
Arbeitsblatt für den Unterricht & Hausaufgaben
Q1. Variant 1: After converting a meter, are the scale divisions on the dial still linear and uniform?
Answer Key: Strictly linear and uniform! Needle deflection remains directly proportional to measured voltage or current.
Q2. Variant 2: If a converted voltmeter systematically reads 5% lower than the standard meter, how to adjust R?
Answer Key: Reading low means undersized current from an oversized multiplier resistor. Slightly reduce the series multiplier resistance.
Q3. Variant 3: What are internal resistances of ideal voltmeters and ammeters? Why?
Answer Key: Ideal voltmeter: infinite (∞) resistance (zero current diversion). Ideal ammeter: zero (0) resistance (zero voltage drop).
Häufige Fragen & typische Missverständnisse
When a converted 3A ammeter hits full scale, did current through the original meter coil increase?
No! Current through the sensitive moving coil is strictly Ig (500μA). The remaining 2.9995A flows through the parallel shunt resistor.
What happens if a voltmeter is mistakenly wired in series like an ammeter?
The circuit effectively opens. Enormous voltmeter resistance restricts current to microamps; the device fails to run while the meter safely reads battery voltage.
What happens if an ammeter is mistakenly wired in parallel across a power supply?
Dead short circuit catastrophe! Sub-ohm ammeter resistance draws immense current, bending the needle, vaporizing shunt resistors, or blowing fuses.
How does an analog multimeter measure resistance, voltage, and current with a single meter movement?
A rotary switch toggles internal topologies: series multipliers for voltage, parallel shunts for current, and internal battery with zeroing pot for ohms.