Introduction

Relevance of the Theme

Electric Current is the blood that circulates through the heart of electrical circuits. It is one of the cornerstones of electromagnetic theory, and its understanding is key to unraveling a variety of phenomena and devices, from the alternating current that powers our homes and industries, to the bright flashes of lightning and the subtle currents that run through our bodies. Without electric current, the study of Electricity would be incomplete.

Contextualization

Electric Current is the sequence of moving electrons. When these electrons are forced to move, we say there is an electric current. This phenomenon is the crucial link between electrical voltage (previously seen) and electrical resistance (to be addressed later). In a closed circuit, voltage (or voltage) forces electrons to move, and resistance offers opposition to this movement. Together, voltage, current, and resistance form Ohm's Law. A full understanding of Electric Current leads us to understand how energy flows through a circuit, and how variables such as resistance can affect the flow of energy. This concept is fundamental to the study of exact sciences and technology at all levels.

Theoretical Development

Components

• Electric Current: Electric current, represented by 'I' in equations, is the flow of electrons through a conductor. The current is measured in amperes (A) and is the amount of electric charge (electrons) that passes through a point in a conductor every second. The movement of electrons is caused by a potential difference (voltage) applied in a circuit.

• Current Intensity: Also known as amperage, it is the term used to express the amount of electric current in a circuit. Represented by 'I', intensity is directly proportional to voltage and inversely proportional to resistance, according to Ohm's Law (I = V/R).

• Conductors: Any material that allows the flow of electrons is called a conductor. Metals like copper and aluminum are excellent conductors, while materials like plastic and glass are insulators and do not allow the passage of electric current.

• Electric Charges: Electric current is a rate of flow of electric charges. Charges mark the presence of an electric force and can be positive (protons) or negative (electrons).

• Electrical Resistance: Electric current is affected by resistance in a circuit. Resistance, represented by 'R', is a property of a component or material that limits the flow of current. The higher the resistance, the lower the current for a given voltage.

Key Terms:

• Ampere (A): Unit of measure of electric current. One ampere corresponds to 1 coulomb of charge passing through a point in a conductor every second.

• Potential Difference (V): Measure of the force that drives electrons in a circuit. Also known as voltage, it is the energy supplied for each unit of charge.

• Resistor (R): Electrical component that introduces resistance in a circuit. Resistance is given by the equation R=V/I, where R is the resistance, V is the voltage, and I is the current.

Examples and Cases:

• Current in a wire: When a battery is connected to a copper wire, the free electrons in the copper start to move, forming an electric current. The amount of current is determined by the battery voltage and the wire resistance.

• Current in a simple circuit: In a circuit with a 9-volt battery and a 3-ohm resistor, the current is calculated by Ohm's Law, I = V/R. Thus, the current in this circuit would be 3 amperes.

• Ohm's Law: This law, I=V/R, illustrates the nature of electric current. Voltage is the force driving the current, resistance is the opposition to the flow (provided by elements like resistors), and current is the result of this balance.

Detailed Summary

Relevant Points

• Understanding Electric Current: The understanding that electric current is the flow of electric charges (measured in Amperes) per unit of time through a conductor is fundamental. This rate of flow of charges is driven by a potential difference (voltage) applied to the circuit.

• Ohm's Law and Current Intensity: Ohm's Law is an indispensable tool for understanding electric current. It defines the current intensity (I) as directly proportional to voltage (V) and inversely proportional to resistance (R). In other words, the current increases with voltage and decreases with resistance.

• Conductors and Resistances: Electric current flows through conductors. Conductors, like metals, allow the movement of electrons. Components with high resistance, like resistors, decrease the flow of current.

• Relationship between Current and Electric Charges: Electric current is actually a rate of flow of electric charges. The presence of positive (protons) or negative (electrons) electric charges is a prerequisite for electric current to exist.

Conclusions

• Electric current is a flow of electric charges (measured in Amperes) that circulates through a conductor when there is a potential difference (voltage) applied.

• Electric current is directly proportional to voltage and inversely proportional to resistance, according to Ohm's Law.

• Electric current can only exist in the presence of electric charges, which can be positive (protons) or negative (electrons).

• The presence of resistance in a circuit can limit the flow of current, as well as the type of material through which the current is passing (conductor or insulator).

Suggested Exercises

1. Consider a circuit with a 12-volt battery and a 4-ohm resistor. How much electric current (in amperes) flows through the resistor?

2. If the resistance of a circuit remains constant and the voltage is increased by half, how will the electric current be affected?

3. Explain how electric current flows in a copper wire when a battery is connected to its terminals. Refer to the battery voltage, wire resistance, and the Ohm's law phrase that describes this situation.