2.5
Transformação da Fonte
A transformação de fontes é uma técnica fundamental empregada na análise de circuitos, oferecendo uma ferramenta valiosa para simplificar circuitos el…
A técnica de transformação de fonte permite a conversão de uma fonte de tensão em série com um resistor em uma fonte de corrente equivalente em paralelo com o resistor ou vice-versa.
Durante a transformação, os valores do resistor no circuito permanecem os mesmos. Usando a lei de Ohm, os valores de tensão ou corrente podem ser determinados.
A seta da fonte de corrente sempre aponta para o terminal positivo da fonte de tensão.
Esta técnica não pode ser aplicada a fontes ideais de tensão e corrente devido às suas características de resistência interna.
Considere um circuito que consiste em uma fonte de tensão, uma fonte de corrente e alguns resistores. Usando a transformação da fonte, a queda de tensão no resistor central pode ser determinada.
Inicialmente, aplique a transformação de origem em ambas as fontes para obter o circuito reduzido.
Agora transforme a fonte de tensão esquerda novamente em uma fonte de corrente. O circuito é ainda mais simplificado em uma única configuração de fonte de corrente.
Usando a fórmula de divisão de corrente, a corrente através do resistor é obtida. Ao substituí-lo na lei de Ohm, a queda de tensão no resistor é obtida.
View the full transcript and gain access to JoVE Core videos
Q1: What is source transformation and how does it simplify circuit analysis?
Source transformation converts a voltage source in series with a resistor into an equivalent current source in parallel with the resistor, or vice versa. This technique simplifies complex circuits by reducing their complexity while maintaining equivalent electrical behavior. The resistor values remain unchanged during transformation, allowing engineers to analyze circuits more efficiently using nodal analysis with voltage sources or other methods.
Q2: Why can't source transformation be applied to ideal voltage and current sources?
Ideal voltage sources have zero internal resistance, while ideal current sources have infinite internal resistance. Source transformation requires non-zero internal resistance to establish equivalence between the two source types. Nonideal sources with finite internal resistance can be transformed, but ideal sources lack the necessary resistance characteristics to create equivalent configurations.
Q3: How do you determine the direction of the current source arrow during transformation?
The current source arrow always points toward the positive terminal of the original voltage source. This directional convention ensures consistency and maintains proper circuit orientation throughout the transformation process. Following this rule prevents errors in circuit analysis and helps maintain the correct polarity relationships in the equivalent circuit.
Q4: What happens to equivalent resistance when sources are deactivated during transformation?
When the original sources are deactivated, the equivalent resistance at the circuit's end terminals remains the same before and after transformation. This principle ensures that the transformed circuit maintains the same electrical characteristics as the original circuit. The resistor values and their configuration preserve the equivalent resistance seen from the circuit terminals.
Q5: How is source transformation used to find voltage drop across a resistor?
Apply source transformation to convert voltage sources into current sources, simplifying the circuit into a single current source configuration. Use the current division formula to determine current through the target resistor. Then substitute this current value into Ohm's law to calculate the voltage drop across the resistor.
Q6: What is the relationship between series and parallel resistances in source transformation?
In source transformation, the series resistance in the voltage source configuration equals the parallel resistance in the current source configuration. When these resistances are equal and the voltage adheres to Ohm's law, the nonideal voltage source becomes equivalent to the nonideal current source. This equivalence ensures that replacing one source with the other does not alter voltage or current characteristics throughout the circuit.
Q7: How does source transformation preserve circuit behavior when replacing sources?
Replacing a nonideal voltage source with its equivalent nonideal current source does not alter the voltage or current characteristics of any element within the circuit. This preservation occurs because both configurations maintain the same equivalent resistance and follow Ohm's law relationships. Source transformation enables circuit simplification while guaranteeing that all element behaviors remain unchanged.