PRIMEIRA LEI DE OHM | ELETRODINÂMICA | AULA 5 - Professor Boaro

Summary

This lesson introduces electric resistors, explaining their crucial role in everyday devices such as showers, hair dryers, and light bulbs. The instructor, Professor Marcelo Boaro, emphasizes the importance of understanding resistors and the first law of Ohm. He covers concepts such as resistance, the calculation of resistance (U/I), and how resistors work in electrical circuits. The lesson also explores the difference between ohmic and non-ohmic resistors, their characteristic curves, and their applications in real-world scenarios. The key takeaway is the formula U = R × I, which is foundational for understanding electric circuits and is essential for students' success in physics.

Takeaways

• 😀 Resistors are common in everyday life, found in appliances like showers, hair dryers, and light bulbs.
• 😀 A resistor's main physical property is electrical resistance, which opposes the flow of electrical current.
• 😀 Ohm's Law is the fundamental principle used to calculate resistance: U = R × I.
• 😀 In Ohm's Law, U represents voltage (measured in volts), R represents resistance (measured in ohms), and I represents current (measured in amperes).
• 😀 The unit of resistance is the ohm (Ω), and resistance is calculated as R = U / I.
• 😀 Ohmic resistors have a constant resistance over a given range of voltage, meaning current increases proportionally with voltage.
• 😀 A graph of voltage versus current for ohmic resistors forms a straight line, indicating a linear relationship.
• 😀 Non-ohmic resistors have a non-linear relationship between voltage and current, meaning doubling voltage doesn't necessarily double current.
• 😀 The resistance of a resistor depends on factors like material, size, and temperature, which can be further explored in later lessons.
• 😀 The teacher stresses the importance of understanding Ohm's Law, as it will be used throughout the entire course of electrical dynamics.

Q & A

What is a resistor and where can it be found in everyday life?

A resistor is an electrical component that resists the flow of electric current. It can be found in various household appliances such as showers, electric grills, hairdryers, and light bulbs.

What is the key difference between the terms 'resistor' and 'resistance'?

The resistor is the physical object, while resistance refers to the property of that object that resists the flow of electric current.

What is the symbol used to represent a resistor in circuit diagrams?

The symbol used for a resistor in electrical circuit diagrams is a zigzag line.

How is the resistance of a resistor calculated?

The resistance is calculated using the formula R = U / I, where R is the resistance, U is the voltage (DDP), and I is the current.

What are the units of resistance, voltage, and current in the International System of Units?

The unit of resistance is the ohm (Ω), voltage is measured in volts (V), and current is measured in amperes (A).

What is the behavior of an ohmic resistor when the voltage changes?

For an ohmic resistor, the resistance remains constant within a specific range of voltage, meaning if the voltage doubles, the current will also double, and if the voltage triples, the current will triple as well.

What does a U vs. I graph for an ohmic resistor look like?

The graph of voltage (U) versus current (I) for an ohmic resistor is a straight line, showing a proportional relationship where the current increases linearly as the voltage increases.

How is the resistance related to the slope of the U vs. I graph?

The resistance is numerically equal to the tangent of the angle of the line in the U vs. I graph, which is the ratio of the voltage (U) to the current (I).

What is the most important formula in electrodynamics, according to the lesson?

The most important formula is U = R × I, where U is the voltage, R is the resistance, and I is the current. This is a key equation used in analyzing electrical circuits.

What is the behavior of a non-ohmic resistor?

In a non-ohmic resistor, the relationship between voltage and current is not proportional. If you double the voltage, the current may not double because the resistance changes, typically due to factors like temperature or material properties.