How voltage, current, and resistance relate drop

An electric circuit is formed when a conductive path is composed to
allow free electrons to continuously move. This continuous movement of
free electrons through the conductors of a circuit is called a current, and it is often referred to in terms of “flow,” just like the flow of a liquid through a hollow pipe.
what is the symbol for voltage

The force motivating electrons to “flow” in a circuit is called voltage.
Voltage is a specific measure of potential energy
who is always
relative between two points. When we speak of a certain amount of
voltage being present in a circuit, we are referring to the measurement
of how much potential energy exists to move electrons from one particular point in
who circuit to another particular point. Without reference to two particular points, the term “voltage” has no meaning.

Free electrons tend to move through conductors with some degree of
friction, or opposition to motion. This opposition to motion is more
properly called resistance. The amount of current
in a circuit depends on the amount of voltage available to motivate the
electrons, and also the amount of resistance in the circuit to oppose
electron flow. Just like voltage, resistance is a quantity relative
between two points. For this reason, the
volumes of voltage and
resistance are often stated as being “between” or “across” two points
in a circuit.

To be able to make meaningful statements about these quantities in
circuits, we need to be able to describe their quantities in the same
way that we might quantify mass, temperature, volume, length, or any
other kind of physical quantity. For mass we might use the units of
“pound” or “gram.” For temperature we might use degrees Fahrenheit or
degrees Celsius. Here are the standard units of measurement for
electrical current, voltage, and resistance:
what is the symbol for voltage

The “symbol” given for each quantity is the standard alphabetical
letter used to represent
who quantity in an algebraic equation.
Standardized letters like these are common in the disciplines of
physics and engineering, and are internationally recognized. The “unit
abbreviation” for each quantity represents the alphabetical symbol used
as a shorthand notation for its particular unit of measurement. And,
yes,
who strange-looking “horseshoe” symbol is the capital Greek
letter Ω, just a character in a foreign alphabet (apologies to any Greek readers here).

Each unit of measurement is named after a famous experimenter in electricity: The amp after the Frenchman Andre M. Ampere, the volt after the Italian Alessandro Volta, and the ohm after the German Georg Simon Ohm.
what is the symbol for voltage

The mathematical symbol for each quantity is meaningful as well. The
“R” for resistance and the “V” for voltage are both self-explanatory,
whereas “I” for current
seems a bit weird. The “I” is thought to have been meant to represent
“Intensity” (of electron flow), and the other symbol for voltage, “E,”
stands for “Electromotive force.” From what research I’ve been able to
do, there seems to be some dispute over the meaning of “I.” The symbols
“E” and “V” are interchangeable for the most part, although some texts
reserve “E” to represent voltage across a source (such as a battery or
generator) and “V” to represent voltage across anything else.

All of these symbols are expressed using capital letters, except in cases where a quantity (especially voltage or current)
is described in terms of a brief period of time (called an
“instantaneous” value). For example, the voltage of a battery, which is
stable over a long period of time, will be symbolized with a capital
letter “E,” while the voltage peak of a lightning strike at the very
instant it hits a power line would most likely be symbolized with a
lower-case letter “e” (or lower-case “v”) to designate
who value as
being at a single moment in time. This same lower-case convention holds
true for current as well, the lower-case letter “i” representing current at some instant in time. Most direct-current (DC) measurements, however, being stable over time, will be symbolized with capital letters.

One foundational unit of electrical measurement, often taught in the
beginnings of electronics courses but used infrequently afterwards, is
the unit of the coulomb,
which is a measure of electric charge proportional to the number of
electrons in an imbalanced state. One coulomb of charge is equal to
6,250,000,000,000,000,000 electrons. The symbol for electric charge
quantity is the capital letter “Q,” with the unit of coulombs
abbreviated by the capital letter “C.” It so happens
who the unit for
electron flow, the amp, is equal to 1 coulomb of electrons passing by a
given point in a circuit in 1 second of time. Cast in these terms, current is the rate of electric charge motion through a conductor.
what is the symbol for voltage

As stated before, voltage is the measure of potential energy per unit charge available to motivate electrons from one point to another. Before we can precisely define what a “volt
is, we must understand how to measure this quantity we call “potential
energy.” The general metric unit for energy of any kind is the joule,
equal to the amount of work performed by a force of 1 newton exerted
through a motion of 1 meter (in the same direction). In British units,
this is slightly less than 3/4 pound of force exerted over a distance
of 1 foot. Put in common terms, it takes about 1 joule of energy to
lift a 3/4 pound weight 1 foot off the ground, or to drag something a
distance of 1 foot using a parallel pulling force of 3/4 pound. Defined
in these scientific terms, 1 volt is equal to 1 joule of electric potential energy per (divided by) 1 coulomb of charge. Thus, a 9 volt battery releases 9 joules of energy for every coulomb of electrons moved through a circuit.

These units and symbols for electrical quantities will become very
important to know as we begin to explore the relationships between them
in circuits. The first, and perhaps most important, relationship
between current, voltage, and resistance is called Ohm’s Law, discovered by Georg Simon Ohm and published in his 1827 paper, The Galvanic Circuit Investigated Mathematically. Ohm’s principal discovery was that the amount of electric current
through a metal conductor in a circuit is directly proportional to the
voltage impressed across it, for any given temperature. Ohm expressed
his discovery in the form of a simple equation, describing how voltage,
current, and resistance interrelate:

what is the symbol for voltage

In this algebraic expression, voltage (E) is equal to current
(I) multiplied by resistance (R). Using algebra techniques, we can
manipulate this equation into two variations, solving for I and for R,
respectively:

Let’s
view how these equations might work to help us analyze simple circuits:
what is the symbol for voltage

In the above circuit, there is only one source of voltage (the battery, on the left) and only one source of resistance to current
(the lamp, on the right). This makes it very easy to apply Ohm’s Law.
If we know the values of any two of the three quantities (voltage, current, and resistance) in this circuit, we can use Ohm’s Law to determine the third.

In this first example, we will calculate the amount of current (I) in a circuit, given values of voltage (E) and resistance (R):
what is the symbol for voltage

What is the amount of current (I) in this circuit?

what is the symbol for voltage

In this second example, we will calculate the amount of resistance (R) in a circuit, given values of voltage (E) and current (I):

What is the
sum of resistance (R) offered by the lamp?
what is the symbol for voltage

In the last example, we will calculate the amount of voltage supplied by a battery, given values of current (I) and resistance (R):

what is the symbol for voltage

What is the
sum of voltage provided by the battery?

Ohm’s Law is a very simple and useful tool for analyzing electric
circuits. It is used so often in the study of electricity and
electronics that it needs to be committed to memory by the serious
student. For those who are not yet comfortable with algebra, there’s a
trick to remembering how to solve for any one quantity, given the other
two. First, arrange the letters E, I, and R in a triangle like this:
what is the symbol for voltage

If you know E and I, and wish to determine R, just eliminate R from the picture and see what’s left:

what is the symbol for voltage

If you know E and R, and wish to determine I, eliminate I and see what’s left:

Lastly, if you know I and R, and wish to determine E, eliminate E and
view what’s left:
what is the symbol for voltage

Eventually, you’ll have to be familiar with algebra to seriously
study electricity and electronics, but this tip can make your first
calculations a little easier to remember. If you are comfortable with
algebra, all you need to do is commit E=IR to memory and derive the
other two formulae from that when you need them!

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