Eletricidade e eletromagnetismo · AP Physics 2 (DC Circuits)

Simulador dinâmico da lei de Ohm

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.

Simulador dinâmico da lei de Ohm e medição volt-ampere: conexões interna e externa

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Dedução ao vivo
Modo projetor
Folha de exercícios A4

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Janela de simulação 3D● 60 FPS

Velocidade:

Predefinições e armadilhas comuns:

Variáveis de controle do experimento

Resistência real Rx

Resistência do amperímetro RA

Resistência do voltímetro RV

Modo de ligação

Deduções e métricas em tempo real

Resistência medida R_med

Erro sistemático relativo

Limite crítico sqrt(RA*RV)

Ligação recomendada

Dedução de fórmulas em tempo real

Fórmula fundamental: --

Substituição de valores: --

Estado físico: --

Ferramenta relacionada: ⚡ Standard Tool: Ohm's Law Calculator ↗

Exemplos clássicos e armadilhas de exame

Worked Problem

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

Derivação passo a passo:

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

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

Derivação passo a passo:

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

Folha de investigação em aula e exercícios

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?

Perguntas frequentes e erros comuns

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.