resolução teste terceiro ano 3

Summary

The video explains how to calculate the number of electrons in a circuit by using the charge and current relationship. It begins by discussing how to calculate the charge from the area of a triangle on a graph of current versus time. The formula for current (I = q/Δt) is applied, and the area of the triangle (base x height / 2) gives the total charge. The calculation is then used to find the number of electrons by dividing the total charge by the charge of a single electron. The final result is expressed in scientific notation, providing a clear step-by-step breakdown of the process.

Takeaways

• 😀 The script explains the process of calculating electric charge using a graph area. The area under the graph represents the total charge.
• 😀 When the current is constant, the formula I = q / Δt is used, where 'q' is charge and 'Δt' is the time interval.
• 😀 The charge can be calculated from the area of the graph, which in this case is a triangle, using the formula for the area of a triangle: base × height / 2.
• 😀 The base of the triangle is given as 10, and the height is 5, resulting in an area of 25 C (Coulombs) for the charge.
• 😀 The total number of electrons is then calculated using the formula: charge = number of electrons × charge of one electron.
• 😀 The number of electrons is found by dividing the total charge (25 C) by the charge of one electron (1.6 × 10^(-19) C).
• 😀 A detailed explanation of dividing decimals is given, including converting the decimal to a non-decimal form for easier calculation.
• 😀 A step-by-step calculation is shown to obtain the result: 25 divided by 1.6 × 10^(-19) results in approximately 15.6 × 10^19 electrons.
• 😀 The script emphasizes that scientific calculations require attention to units and careful handling of powers of 10.
• 😀 The final number of electrons, expressed as 15.6 × 10^19, is the correct answer to the problem posed in the script.
• 😀 A cautionary note is included to ensure that the calculations are done correctly, especially when handling powers of 10 and scientific notation.

Q & A

What is the formula used to calculate current when it is constant?

The formula for current when it is constant is I = Q / Δt, where I is the current, Q is the charge, and Δt is the time interval.

How do you calculate the area under a graph when the graph is a triangle?

To calculate the area under a graph that forms a triangle, you use the formula: Area = (Base * Height) / 2.

What are the base and height values of the triangle in this example?

In this example, the base of the triangle is 10, and the height of the triangle is 5.

How do you calculate the total charge in this scenario?

The total charge is calculated by finding the area of the triangle, which is 10 * 5 / 2 = 25 Coulombs.

How do you calculate the number of electrons from the total charge?

To calculate the number of electrons, divide the total charge by the elementary charge (the charge of one electron), using the formula: N = Q / e, where Q is the total charge and e is the charge of one electron (1.6 × 10^-19 C).

What is the elementary charge of an electron?

The elementary charge of an electron is 1.6 × 10^-19 Coulombs.

How do you simplify the calculation when dividing by a decimal in this problem?

To simplify the calculation when dividing by a decimal, you can eliminate the decimal by multiplying both the numerator and denominator by a power of 10 (in this case, multiplying by 10 to make the denominator a whole number).

What is the result of dividing 25 by 1.6 × 10^-19?

The result of dividing 25 by 1.6 × 10^-19 is approximately 15.6 × 10^19.

Why is the final answer expressed as 15.6 × 10^19 instead of 15.6 × 10^-19?

The final answer is expressed as 15.6 × 10^19 because when dividing by 10^-19, the exponent of -19 is moved to the positive side, resulting in 10^19.

What is the significance of calculating the number of electrons in this context?

Calculating the number of electrons is important to understand the total amount of charge transferred, which is useful for analyzing the behavior of electrical circuits and understanding the flow of electricity.