index        previous        next

Ohm's Law

Download for Macintosh or for PC.

Ohm's Law says that the voltage (E, in volts) across a resistor is given by the product of the current (I, in amps) flowing through it and its resistance (R, in ohms):

E = IR, also I=E/R and R=E/I

Ohm's law is very simple and it may seem trivial, but its importance in electronics can not be underestimated.

The power (P, in watts) dissipated by the resistor is given by P = IE. This must not exceed the power rating of the resistor or else the resistor will may overheat and be burned up.

Use the slider to change the value of the resistor. Change the battery voltage by typing into the box to the left of the battery symbol. The current and power will be calculated and displayed by the simulation. If the power exceeds 0.5 watts, a warning message will be displayed by the simulation. Resistors with 0.5 watt maximun power rating are the most common type, but higher power resistors are available; usually they are physically larger and cost more that lower-power resistors.

Return to the Index.

This page is maintained by Prof. T. C. O'Haver , Department of Chemistry and Biochemistry, The University of Maryland at College Park. Comments, suggestions and questions should be directed to Prof. O'Haver at
Unique page visits since May 17, 2008: