Electrical Engineering: Basic Concepts (3 of 7) Electric Current (Conventional vs Electrical Flow)
Summary
TLDRThe 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
🔋 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.
Mindmap
Keywords
💡Conventional Current
💡Electron Flow
💡Positive and Negative Charges
💡I Triple E Convention
💡Coulombs
💡Ampere
💡Unit Charge
💡Charge
💡Differential Equation
💡Integral
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
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