Electric current

Electric current definition and calculations.

Electric current definition

Electrical current is the flow rate of electric charge in electric field, usually in electrical circuit.

Using water pipe analogy, we can visualize the electrical current as water current that flows in a pipe.

The electrical current is measured in ampere (amp) unit.

Electric current calculation

Electrical current is measured by the rate of electric charge flow in an electrical circuit:

i(t) = dQ(t) / dt

The momentary current is given by the derivative of the electric charge by time.

i(t) is the momentary current I at time t in amps (A).

Q(t) is the momentary electric charge in coulombs (C).

t is the time in seconds (s).

When the current is constant:

I = ΔQ / Δt

I is the current in amps (A).

ΔQ is the electric charge in coulombs (C), that flows at time duration of Δt.

Δt is the time duration in seconds (s).

Example

When 5 coulombs flow through a resistor for duration of 10 seconds,

the current will be calculated by:

I = ΔQ / Δt  = 5C / 10s = 0.5A

Current calculation with Ohm's law

The current IR in anps (A) is equal to the resistor's voltage VR in volts (V) divided by the resistance R in ohms (Ω).

IR = VR / R

Current direction
current type from to
Positive charges + -
Negative charges - +
Conventional direction + -

Current in series circuits

Current that flows through resistors in series is equal in all resistors - just like water flow through a single pipe.

ITotal = I1 = I2 = I3 =...

ITotal - the equivalent current in amps (A).

I1 - current of load #1 in amps (A).

I2 - current of load #2 in amps (A).

I3 - current of load #3 in amps (A).

Current in parallel circuits

Current that flows through loads in parallel - just like water flow through parallel pipes.

The total current ITotal is the sum of the parallel currents of each load:

ITotal = I1 + I2 + I3 +...

ITotal - the equivalent current in amps (A).

I1 - current of load #1 in amps (A).

I2 - current of load #2 in amps (A).

I3 - current of load #3 in amps (A).

Current divider

The current division of resistors in parallel is

RT = 1 / (1/R2 + 1/R3)

or

I1 = IT × RT / (R1+RT)

Kirchhoff's current law (KCL)

The junction of several electrical components is called a node.

The algebraic sum of currents entering a node is zero.

Ik = 0

Alternating Current (AC)

Alternating current is generated by a sinusoidal voltage source.

Ohm's law

IZ = VZ / Z

IZ  - current flow through the load measured in amperes (A)

VZ - voltage drop on the load measured in volts (V)

Z  - impedance of the load measured in ohms (Ω)

Angular frequency

ω = 2π f

ω - angular velocity measured in radians per second (rad/s)

f  - frequency measured in hertz (Hz).

Momentary current

i(t) = Ipeak sin(ωt+θ)

i(t)      - momentary current at time t, measured in amps (A).

Ipeak - maximal current (=amplitude of sine), measured in amps (A).

ω      - angular frequency measured in radians per second (rad/s).

t        - time, measured in seconds (s).

θ       - phase of sine wave in radians (rad).

RMS (effective) current

IrmsIeffIpeak / √2 ≈ 0.707 Ipeak

Peak-to-peak current

Ip-p = 2Ipeak

Current measurement

Current measurement is done by connecting the ammeter in series to the measured object, so all the measured current will flow through the ammeter.

The ammeter has very low resistance, so it almost does not affect the measured circuit.


Currently, we have around 5663 calculators, conversion tables and usefull online tools and software features for students, teaching and teachers, designers and simply for everyone.

You can find at this page financial calculators, mortgage calculators, calculators for loans, calculators for auto loan and lease calculators, interest calculators, payment calculators, retirement calculators, amortization calculators, investment calculators, inflation calculators, finance calculators, income tax calculators, compound interest calculators, salary calculator, interest rate calculator, sales tax calculator, fitness & health calculators, bmi calculator, calorie calculators, body fat calculator, bmr calculator, ideal weight calculator, pace calculator, pregnancy calculator, pregnancy conception calculator, due date calculator, math calculators, scientific calculator, fraction calculator, percentage calculators, random number generator, triangle calculator, standard deviation calculator, other calculators, age calculator, date calculator, time calculator, hours calculator, gpa calculator, grade calculator, concrete calculator, subnet calculator, password generator conversion calculator and many other tools and for text editing and formating, downloading videos from Facebok (we built one of the most famous Facebook video downloader online tools). We also provide you online downloanders for YouTube, Linkedin, Instagram, Twitter, Snapchat, TikTok and other social media sites (please note we does not host any videos on its servers. All videos that you download are downloaded from Facebook's, YouTube's, Linkedin's, Instagram's, Twitter's, Snapchat's, TikTok's CDNs. We also specialise on keyboard shortcuts, ALT codes for Mac, Windows and Linux and other usefull hints and tools (how to write emoji online etc.)

There are many very usefull online free tools and we would be happy if you share our page to others or send us any suggestions for other tools which will come on your mind. Also in case you find any of our tools that it does not work properly or need a better translation - please let us know. Our tools will make your life easier or simply help you to do your work or duties faster and in more effective way.

These below are the most commonly used by many users all over the world.

And we are still developing more. Our goal is to become the one-stop, go-to site for people who need to make quick calculations or who need to find quick answer for basic conversions.

Additionally, we believe the internet should be a source of free information. Therefore, all of our tools and services are completely free, with no registration required. We coded and developed each calculator individually and put each one through strict, comprehensive testing. However, please inform us if you notice even the slightest error – your input is extremely valuable to us. While most calculators on Justfreetools.com are designed to be universally applicable for worldwide usage, some are for specific countries only.


Page Id: 1193

This website uses cookies to improve your experience, analyze traffic and display ads. Learn more