ASSOCIAÇÃO DE RESISTORES: em série e em paralelo | Cortes dos Aulões do Enem | Física | Antônio

Summary

This video script covers essential concepts on resistor combinations for the ENEM exam, focusing on series and parallel associations. It explains the behavior of electric currents and voltages in each type of circuit, highlighting key formulas like Ohm's Law and rules for calculating total resistance and current. In series circuits, the same current flows through all resistors while the voltage divides among them, whereas in parallel circuits, the voltage remains constant, and the current splits depending on the resistance. Understanding these concepts is crucial for solving circuit problems efficiently.

Takeaways

• 😀 **Resistor association in series:** When resistors are connected in series, the current is the same through each resistor, but the voltage divides among them.
• 😀 **Current in series:** The total current (I_total) is the same across all resistors in a series circuit (I1 = I2 = I3).
• 😀 **Voltage in series:** The total voltage of the power source is the sum of the voltages across each resistor in the series circuit (U_total = U1 + U2 + U3).
• 😀 **Calculating equivalent resistance in series:** The total resistance in a series circuit is the sum of the individual resistances (R_eq = R1 + R2 + R3).
• 😀 **Ohm's law for series circuits:** To find the total current in a series circuit, use Ohm’s law: I = U_total / R_eq.
• 😀 **Resistor association in parallel:** When resistors are connected in parallel, the voltage across each resistor is the same, but the current divides according to the resistance of each resistor.
• 😀 **Current in parallel:** The total current entering the node is the sum of the currents through each parallel resistor (I_total = I1 + I2).
• 😀 **Voltage in parallel:** The voltage across each resistor in a parallel circuit is equal to the total voltage of the source (U_total = U1 = U2).
• 😀 **Calculating equivalent resistance in parallel:** For two resistors in parallel, the equivalent resistance is calculated as R_eq = (R1 * R2) / (R1 + R2).
• 😀 **Formula for total current in parallel:** To calculate the total current in a parallel circuit, use Ohm’s law: I = U / R_eq, where R_eq is the equivalent resistance.

Q & A

What is the main topic discussed in the transcript?

The main topic is the association of resistors, specifically in series and parallel configurations, which is a key concept in electrical circuits and often appears in exams like ENEM.

What happens to the current in a series resistor circuit?

In a series circuit, the current is the same throughout all resistors. The total current that leaves the power source flows through each resistor without splitting.

How is the total resistance in a series circuit calculated?

The total resistance in a series circuit is simply the sum of the individual resistances. For example, if resistors of 1, 2, and 3 ohms are in series, the total resistance is 1 + 2 + 3 = 6 ohms.

What is the relationship between voltage, resistance, and current in a series circuit?

In a series circuit, the total voltage is the sum of the voltage drops across each resistor. Ohm's Law (V = IR) is used to determine the voltage drop across each resistor based on its resistance and the current.

How do you calculate the current in a series circuit?

To calculate the current in a series circuit, use Ohm's Law. First, find the total resistance, then use the formula I = V / R, where V is the total voltage and R is the total resistance.

What is the significance of the current being constant in a series circuit?

In a series circuit, since there is only one path for the current to flow, the current remains constant throughout all the resistors. This means that the same current flows through each component of the series circuit.

How does a parallel resistor circuit differ from a series one in terms of current?

In a parallel circuit, the current splits at the junction where the resistors meet. The current passing through each resistor depends on the individual resistances, and the total current is the sum of the currents through each parallel resistor.

What is the total voltage across resistors in parallel?

In a parallel circuit, the voltage across each resistor is the same and equal to the voltage of the power source. For example, if the power source is 12 volts, each resistor in parallel will have 12 volts across it.

How is the equivalent resistance calculated in a parallel circuit?

In a parallel circuit, the equivalent resistance (R_eq) is found by taking the reciprocal of the sum of the reciprocals of the individual resistances. For two resistors, the formula is: 1/R_eq = 1/R1 + 1/R2. For more than two resistors, the formula extends similarly.

What happens when two resistors of 3 ohms and 6 ohms are connected in parallel?

When two resistors of 3 ohms and 6 ohms are connected in parallel, the equivalent resistance is calculated using the formula: R_eq = (3 * 6) / (3 + 6) = 18 / 9 = 2 ohms.

What is the current distribution in a parallel circuit with two resistors of 3 ohms and 6 ohms connected to a 12V source?

In a parallel circuit with a 12V source, the current is divided between the resistors based on their resistance. For the 3-ohm resistor, the current is 12V / 3Ω = 4A, and for the 6-ohm resistor, the current is 12V / 6Ω = 2A. The total current is the sum of these, which is 6A.

What is the importance of the Law of Junctions (Law of Nodes) in parallel circuits?

The Law of Junctions states that the total current entering a junction (node) is equal to the total current leaving. This law ensures that the sum of the currents through the resistors in parallel will be equal to the current coming out of the power source.