Electrical resistance definition and calculations.

## Resistance definition

Resistance is an electrical quantity that measures how the device or material reduces the electric current flow through it.

The resistance is measured in units of ohms (Ω).

If we make an analogy to water flow in pipes, the resistance is bigger when the pipe is thinner, so the water flow is decreased.

## Resistance calculation

The resistance of a conductor is resistivity of the conductor's material times the conductor's length divided by the conductor's cross sectional area.

R is the resistance in ohms (Ω).

ρ* *is the resistivity in ohms-meter (Ω×m)

l is the length of the conductor in meter (m)

A is the cross sectional area of the conductor in square meters (m^{2})

It is easy to understand this formula with water pipes analogy:

- when the pipe is longer, the length is bigger and the resistance will increase.
- when the pipe is wider, the cross sectional area is bigger and the resistance will decrease.

### Resistance calculation with ohm's law

*R* is the resistance of the resistor in ohms (Ω).

*V* is the voltage drop on the resistor in volts (V).

*I* is the current of the resistor in amperes (A).

### Temperature effects of resistance

The resistance of a resistor increases when temperature of the resistor increases.

*R*_{2} = *R*_{1 }
× ( 1 + α(*T*_{2 }-* T*_{1}) )

*R*_{2} is the resistance at temperature T_{2} in ohms (Ω).

*R*_{1} is the resistance at temperature T_{1} in ohms (Ω).

*α* is the temperature coefficient.

### Resistance of resistors in series

The total equivalent resistance of resistors in series is the sum of the resistance values:

*R _{Total}* =

*R*

_{1}+

*R*

_{2}+

*R*

_{3}+...

### Resistance of resistors in parallel

The total equivalent resistance of resistors in parallel is given by:

### Measuring electrical resistance

Electrical resistance is measured with ohmmeter instrument.

In order to measure the resistance of a resistor or a circuit, the circuit should have the power supply turned off.

The ohmmeter should be connected to the two ends of the circuit so the resistance can be read.

### Superconductivity

Superconductivity is the drop of resistance to zero at very low temperatures near 0ºK.

Currently, we have around 1977 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.

- Free online calculators and tools
- Time zones/Clocks/Dates calculators
- Free online units conversion tools
- Free online web design tools
- Free online electricity & electronics tools
- Mathematics
- Online Tools
- Text Tools
- PDF Tools
- Code
- Ecology
- Others
- Basic Electrical Terms
- Electrical & Electronic Units
- Electronic Components
- Electrical & Electronic Symbols
- Electronic Circuit Laws
- Electric charge
- Electric current
- Electric power
- Electric power efficiency
- Electrical resistance
- Electrical voltage
- Power factor

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.