Электричество и магнетизм · AP Physics 2 (DC Circuits)

Симулятор закона Ома и вольт-амперной характеристики

Q: Does Ohm's law apply universally? When does it fail?

Strictly for ohmic resistors. It fails for non-ohmic devices (motors, electrolysis cells, diodes) where electrical energy converts to work or chemistry.

Q: Why does volt-ampere measurement always carry systematic error? How to achieve zero error?

Real meters are non-ideal. True zero-error measurement requires a Wheatstone bridge or Kelvin 4-wire sensing.

Q: How does temperature affect metal vs semiconductor resistance differently?

Metals have positive temperature coefficient (PTC, R rises with heat). Semiconductors have negative coefficient (NTC, R drops exponentially).

Q: What is typical human body resistance? Why is 36V the legal safety threshold?

Wet human skin drops to ~1000Ω. Lethal threshold is ~30mA. U = IR = 30mA * 1000Ω = 30V, establishing the 36V safety ceiling.

Динамический симулятор закона Ома и вольт-амперного метода измерения сопротивления

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Печатный лист A4

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Скорость:

Пресеты и типичные ловушки:

Параметры эксперимента

Истинное сопротивление Rx

Сопротивление амперметра RA

Сопротивление вольтметра RV

Схема включения

Расчёты и показатели в реальном времени

Измеренное сопротивление R_изм

Относительная систематическая погрешность

Критическое значение sqrt(RA*RV)

Рекомендуемая схема

Вывод формул в реальном времени

Основная формула: --

Подстановка значений: --

Физическое состояние: --

Связанный инструмент: ⚡ Standard Tool: Ohm's Law Calculator ↗

Разбор типовых задач и анализ экзаменационных ошибок

Worked Problem

Условие задачи: Rx ≈ 10Ω, RA = 0.2Ω, RV = 2000Ω. Choose internal or external wiring. Does it read high or low?

Пошаговый вывод формул:

Critical R0 = sqrt(0.2*2000) = 20Ω. Since Rx < 20Ω (small resistor), select external wiring. Voltmeter current diversion makes R_meas read low.

Worked Problem

Условие задачи: A conductor passes 0.5A at 6V. What is its resistance? What if voltage drops to 0V?

Пошаговый вывод формул:

R = 6/0.5 = 12Ω. At 0V, resistance remains 12Ω! Resistance is an intrinsic physical property independent of voltage.

Рабочий лист для урока и домашние задания

Q1. Variant 1: In testing I vs U relationship, what parameter must be kept constant? What is the rheostat's function?

Q2. Variant 2: How does the "touch test" empirical method identify optimal wiring without knowing meter resistances?

Q3. Variant 3: A uniform wire is folded in half and twisted together. What is the new resistance ratio?

Часто задаваемые вопросы и типичные заблуждения

Does Ohm's law apply universally? When does it fail?

Strictly for ohmic resistors. It fails for non-ohmic devices (motors, electrolysis cells, diodes) where electrical energy converts to work or chemistry.

Why does volt-ampere measurement always carry systematic error? How to achieve zero error?

Real meters are non-ideal. True zero-error measurement requires a Wheatstone bridge or Kelvin 4-wire sensing.

How does temperature affect metal vs semiconductor resistance differently?

Metals have positive temperature coefficient (PTC, R rises with heat). Semiconductors have negative coefficient (NTC, R drops exponentially).

What is typical human body resistance? Why is 36V the legal safety threshold?

Wet human skin drops to ~1000Ω. Lethal threshold is ~30mA. U = IR = 30mA * 1000Ω = 30V, establishing the 36V safety ceiling.