License Info
Image Use
Custom Photos
Site Info
Contact Us

Visit Science,
Optics, & You

The Galleries:

Photo Gallery
Silicon Zoo
Chip Shots
DNA Gallery
Amino Acids
Religion Collection
Cocktail Collection
Screen Savers
Win Wallpaper
Mac Wallpaper
Movie Gallery

Ohm's Law

Georg Simon Ohm (1787-1854) formulated the relationships among voltage, current, and resistance as follows:

The current in a circuit is directly proportional to the applied voltage and inversely proportional to the resistance of the circuit.

The circuit below demonstrates these relationships.

  • Click on the resistance slider to change resistors.
  • Click on the voltage slider to adjust voltage of the variable power supply.

Mathematically Ohm's law can be written as:

I = E/R

where I is current in amperes, E is the applied voltage in volts, and R is resistance in ohms.

This circuit contains an ammeter measuring current flow in milliamperes. Notice that as you increase voltage, current flow increases. As you increase resistance, current flow decreases.

It is important to note that resistance cannot be changed by changing voltage or current. Resistance in a circuit is a physical constant. Resistance in a circuit can only be changed by changing components or resistors rated at more or fewer ohms. The changing of resistance in this circuit simulates the physical changing of resistors with different ratings.

Discover how resistors are color coded in our Interactive Java Resistors Tutorial.


Questions or comments? Send us an email.
© 1995-2022 by Michael W. Davidson and The Florida State University. All Rights Reserved. No images, graphics, software, scripts, or applets may be reproduced or used in any manner without permission from the copyright holders. Use of this website means you agree to all of the Legal Terms and Conditions set forth by the owners.
This website is maintained by our
Graphics & Web Programming Team
in collaboration with Optical Microscopy at the
National High Magnetic Field Laboratory.
Last Modification: Wednesday, Jun 07, 2017 at 12:03 PM
Access Count Since April 14, 1999: 563673