Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Ohm's Law

Voltage, current and resistance

Sponsored Links

Ohm's law states that

"the current through a conductor between two points is directly proportional to the potential difference or voltage across the two points, and inversely proportional to the resistance between them".

Ohm's law can be expressed as 

I = U / R                     (1)

where 

I = current (ampere, A)

U = electrical potential (volts, V)

R = resistance (ohms, Ω)

Example - Ohm's law

A 12 volt battery supplies power to a resistance of 18 ohms. The current in the elctrical circuit can be calculated as

I = (12 volts) / (18 ohm)

    = 0.67 ampere

ohm's law

Equivalent Expressions

Ohm's law (1) can also be expressed as

U = R I                         (2)

or 

R = U / I                       (3)

ohms law - voltage, resistance and current diagram

print Ohm's Law diagram!

Example - Electric Circuit Resistance

A current of 1 ampere is flowing through a 230 V electric circuit. From the diagram above this indicates resistance 

R ≈ 220 Ω

This can alternatively be calculated with Ohm's law

R = (230 V) / (1 A)

   = 230 Ω

Example - Ohm's Law and Multiples and Submultiples

Currents, voltages and resistances in electric circuits may often be very small or very large - so multiples and submultiples are often used. 

The voltage required applied to a 3.3 kΩ resistor to generate a current of 20 mA can be calculated as

U = (3.3 kΩ) (1000 Ω/kΩ) (20 mA) (10-3 A/mA)

   = 66 V

Power

Electric power can be expressed as 

P = U I

  = R I2 

  = U2 / R                     (4)

where 

P = electrical power (watts, W)

Example - Power Consumed

The power consumed in the 12V electrical circuit above can be calculated as

P = (12 volts)2 / (18 ohm)

   =  8 W

Example - Power and Electrical Resistance

A 100 W electric light bulb is connected to a 230 V supply. The current flowing can be calculated by reorganizing (4) to

I = P / U

  = (100 W) / (230 V)

  = 0.43 ampere

The resistance can be calculated by reorganizing (4) to

R = U2 / P

   = (230 V)2 / (100 W) 

   = 529 Ω

Sponsored Links

Related Topics

Related Documents

Tag Search

  • en: ohm law current voltage ampere volt power
Sponsored Links

Search the Engineering ToolBox

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse!

Translate this page to
About the Engineering ToolBox!

Privacy

We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.

Citation

This page can be cited as

  • Engineering ToolBox, (2010). Ohm's Law. [online] Available at: https://www.engineeringtoolbox.com/ohms-law-d_1658.html [Accessed Day Mo. Year].

Modify access date.

. .

close

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Scientific Online Calculator

Scientific Calculator

12 14

Sponsored Links
.