Electrical Engineering: Basic Concepts (3 of 7) Electric Current (Conventional vs Electrical Flow)

Summary

The video script delves into the intricacies of electron flow and current direction in physics and engineering. It explains the historical convention of current direction from positive to negative, attributed to Benjamin Franklin, despite modern understanding that electrons, which are negatively charged, actually move in the opposite direction. The script clarifies the difference between conventional current and electron current, emphasizing the importance of the conventional model for practical applications. It also defines current mathematically as the rate of charge flow over time, measured in amperes, and introduces the concept of coulombs as a unit of charge. The script serves as a foundational guide to understanding current in electronic circuits.

Takeaways

• 🔋 The conventional direction of current is from the positive to the negative end of a power source, as established by Benjamin Franklin.
• 🔬 Historically, it was assumed that positive charges flowed into the circuit, but modern science has shown that it's actually the negative charges (electrons) that move.
• 📚 The term 'conventional current' refers to the flow from positive to negative, while 'electron current' or 'negative current' flows from negative to positive.
• ⚖️ Current is defined by the differential equation I = dQ/dt, where I is the current, dQ is the change in charge, and dt is the change in time.
• 🔢 The unit of current, the ampere (amp), is defined as one coulomb of charge passing a point per second.
• ⚛️ A coulomb is a measure of electric charge, equal to the charge of approximately 6.24 x 10^18 electrons or protons.
• 🤔 The concept of charge can be confusing because while electrons carry a negative charge, the conventional current is considered positive.
• 🧮 To calculate the total charge that has passed a point in a circuit, you integrate the current over time: Q = ∫ I dt from 0 to T.
• 📈 If the current is not constant, the total charge is found by integrating the variable current over the time period of interest.
• 💡 Understanding the direction of conventional current as positive to negative, despite electrons moving in the opposite direction, is crucial for following electrical principles.

Q & A

What is the conventional direction of current flow?

The conventional direction of current flow is from the positive end of the power source to the negative end of the power source.

Who set up the concept of conventional current?

The concept of conventional current was set up by Benjamin Franklin.

What assumption did early scientists make about the direction of current?

Early scientists assumed that positive charges moved through the circuit, following the conventional current direction from positive to negative.

What is the actual direction in which electrons flow in a circuit?

Electrons, which are negatively charged, flow from the negative end of the power source to the positive end through the circuit.

How is current defined in terms of charge and time?

Current is defined as the amount of charge passing a particular point in a circuit per unit of time, typically measured in coulombs per second (amps).

What is the value of one Coulomb of charge in terms of elementary charges?

One Coulomb of charge is equal to approximately 6.24 x 10^18 unit charges, such as the charge of an electron or a proton.

How is current represented when it is a variable quantity?

When current is variable, the total charge that passes a point in the circuit is calculated as the integral of the current over time, ∫ I(t) dt.

Why do we refer to electron flow as 'negative current'?

Electron flow is called 'negative current' because electrons, which have a negative charge, move in the opposite direction to the conventional current.

What is the relationship between coulombs and amps?

One ampere of current represents one coulomb of charge passing through a point in the circuit per second.

Why is it useful to maintain the conventional current direction in discussions, despite the actual flow of electrons being opposite?

It is useful to maintain the conventional current direction for consistency and clarity in communication, while understanding that electron flow (negative current) moves in the opposite direction.

Outlines

00:00

🔋 Understanding Electron Current Direction

This paragraph discusses the concept of current in the context of electron flow. It clarifies the historical misunderstanding regarding the direction of current, which was initially thought to flow from the positive to the negative terminal of a power source, as proposed by Benjamin Franklin. However, modern science has established that it is the negatively charged electrons that move, effectively creating a current that flows from the negative to the positive terminal. Despite this, the conventional current direction is still taught as positive to negative for practical reasons. The paragraph also explains the definition of current as the rate of charge flow, measured in coulombs per second (amps), and introduces the concept of charge integration over time to calculate total charge passing a point in a circuit.

Keywords

💡Conventional Current

Conventional current refers to the historical assumption that electric current flows from the positive to the negative terminal of a power source. This concept was established by Benjamin Franklin and is still widely taught despite the fact that it contradicts the actual movement of electrons, which are negatively charged. In the video, the conventional current is mentioned as the starting point for understanding current direction, highlighting the difference between the historical model and the modern understanding of electron flow.

💡Electron Flow

Electron flow is the actual movement of electrons, which are negatively charged particles, through a conductor. Contrary to the conventional current, electrons move from the negative to the positive terminal of a power source. The video explains that while conventional current is taught for simplicity, the real current, or electron current, flows in the opposite direction, which is a crucial distinction for understanding the true nature of electric current.

💡Positive and Negative Charges

Positive and negative charges are fundamental concepts in electricity and magnetism. Positive charges were historically thought to flow from the positive to the negative terminal of a power source, as per the conventional current model. However, modern science has established that it is the negatively charged electrons that move, creating the flow of electric current. The video script clarifies this distinction and its importance in the study of electronics.

💡I Triple E Convention

The I Triple E Convention, or the conventional current direction, is a term used in the video to describe the historical assumption that current flows from the positive to the negative terminal. This convention is named after the Institute of Electrical and Electronics Engineers (IEEE), which has standardized this direction for the sake of consistency in electrical engineering. The video emphasizes that while this is the conventional teaching, it is not the actual direction of electron flow.

💡Coulombs

Coulombs are the unit of electric charge, named after the French physicist Charles-Augustin de Coulomb. In the video, coulombs are used to quantify the amount of charge passing a point in an electric circuit per unit time, which is essential for defining electric current. The script mentions that one coulomb of charge is equivalent to the charge of approximately 6.24 x 10^18 electrons, illustrating the scale at which electric charges are measured.

💡Ampere

The ampere (symbol: A) is the unit of electric current, defined as the flow of one coulomb of charge per second. The video explains that when one ampere of current flows through a circuit, it means that one coulomb of charge passes a given point every second. This unit is central to the discussion of electric current and its measurement.

💡Unit Charge

The unit charge refers to the smallest quantity of electric charge that is considered indivisible in the context of classical physics. In the video, it is explained that the charge of a single electron or proton is considered the unit charge. This concept is important for understanding the scale of electric charge and how it relates to the flow of current in a circuit.

💡Charge

Charge, in the context of the video, refers to the property of matter that causes it to experience a force when placed in an electromagnetic field. It is quantified in coulombs and is the basis for the flow of electric current. The script discusses how the charge passing a point in a circuit can be calculated by integrating the current over time, which is a fundamental concept in electrical engineering.

💡Differential Equation

A differential equation is a mathematical equation that relates a function to its derivatives. In the video, the definition of current is given by a differential equation, where the current (I) is equal to the change in charge (Q) per unit time (t). This equation is crucial for understanding how current is calculated and its relation to the movement of charge in a circuit.

💡Integral

In the context of the video, an integral is used to calculate the total charge that has passed a point in a circuit over a period of time. If the current is not constant, the integral of the current with respect to time (∫I dt) from zero to a certain time T is used to find the total charge. This mathematical concept is essential for understanding the accumulation of charge in an electric circuit.

Highlights

The conventional direction of current is from the positive to the negative end of a power source.

Benjamin Franklin's claim that positive charges flow into the circuit established the conventional current concept.

Current is actually the movement of negative charges, specifically electrons.

The I Triple E convention is used to define the conventional direction of current as positive to negative.

Electrons, which form the negative current, actually move in the opposite direction of the conventional current.

The definition of current is the amount of charge passing a point per unit time.

Current is measured in amperes (amps), where 1 amp equals 1 Coulomb of charge passing per second.

A Coulomb is a unit of electric charge, equivalent to the charge of approximately 6.24 x 10^18 elementary charges.

An electron's charge is considered a single unitary charge, the simplest in the universe.

The charge of an electron is used as the basis for the unit of charge, the Coulomb.

The total charge that has passed a point in a circuit can be calculated by integrating the current over time.

For variable currents, the total charge is found by integrating the current with respect to time from zero to T.

Understanding that current is the flow of positive charge from the positive to the negative end of a battery is crucial for following electrical concepts.

The concept of current is fundamental to grasping the principles discussed in subsequent videos.

The transcript clarifies the difference between conventional current direction and the actual movement of electrons.

The historical context of current direction is provided, highlighting Franklin's influence on its definition.

The importance of distinguishing between conventional current and electron flow for circuit analysis is emphasized.

Transcripts

welcome to electron line one of the most

confusing aspects of electron

engineering versus basic science and

physics when we talk about current is

what is the direction of the current

well the conventional direction the

current is that current flows from a

power source and from the positive end

of the power source to the negative end

of the power source that's the

conventional current that's gate that's

basically the current concept set up by

Benjamin Franklin

he claimed that this positive charges

loan to the circuit however at the time

we didn't understand what the positive

and negative charges were we knew there

were positive charges we knew there were

negative charges we didn't know which

ones were flowing through the circuit

the assumptions made lasers called the

positive charges move into the circuit

we would call that the I Triple E

convention it is the conventional

direction of the current from positive

to negative however we all now realize

that it's the negative charge that are

actually doing the moving it's the

negative electrons in the atoms of

material that are moving to the circuit

in essence the current the real current

the real charges are moving in the

opposite direction from the negative end

of the battery to the positive end of

the battery through the load resistor

what we're going to do from now on is

we're going to assume that the positive

current the conventional current is

flowing to indeed from the positive to

negative side while we understand that

the electrons are flowing the opposite

direction and the electrons and form the

negative current so that way we're

always safe we can say the conventional

current runs from or flows from positive

to negative and the electron current

flows from negative to positive and we

call that therefore the negative current

the definition of the current is defined

here by this differential equation that

is equal to the change in the charge per

unit time we really don't mean that

change we mean the amount of charge a

slowing past past a particular point if

we take any point on the circuit and

wipes current going by that point we can

say that the current flow is equal to

the amount of charge that passes that

point per unit time the charge is

usually indicated in terms of coulombs

in the time in seconds so coulombs per

second then gives us amps or ampair

we use symbol a to indicate the amount

of current that we have one end is

determined or defined by the ratio of

one Coulomb per second when you know we

have a current flow of one amp you know

that there's one Coulomb of charges

passing that point every single second a

Coulomb of charge is equal to six point

two four times ten to the eighteenth

unit charges the unit charge of course

the charge we have in a single Ektron or

a single proton now here again is where

people get confused they say well if the

charge is positive and yet you indicate

negative charges electron charges how

can you justify that an electron charge

is simply a unitary charge the simplest

charge in universe therefore we call an

electron charge a single charge and a

Coulomb has six point to four times ten

to the eighteenth of those again we

think of coulombs as positive we think

of current as positive charge flowing

finally if you want to then calculate

how much charges has gone past a certain

point in the circuit the charges past

that point is equal to the integral of

the current at that point times DT

integrated from zero to T so how much

current has flown over a certain amount

of time especially if I is not a

constant but a variable then of course

you want to keep track of that and the

total charge will then simply be the

integral of the current times DT that's

the basic concept of current from now on

we realize current is positive charge

flowing from the positive end of the

battery to the negative end of the

battery if we all keep that in mind then

it will be a lot easier to follow the

videos that are to come

and that's how we look at current