How To Calculate Voltage By Spark Gaps

You can calculate the voltage needed for electricity to jump across a spark gap with a simple formula: voltage equals the air gap length in centimeters times 30,000. Air is normally an electrical insulator; electricity can't jump out of a wall socket and shock you because the surrounding air does not conduct it. But very high voltages have enough energy to turn air into a conductor, allowing electricity to jump the gap. To calculate a spark gap voltage, first measure the gap with a ruler, then use the distance formula mentioned above to find the voltage.

Step 1

Turn off all power to the spark gap apparatus. For example, to measure a spark plug, turn off the engine and remove the plug.

Step 2

Measure the distance in centimeters between the electrodes in the spark gap with the ruler. For a spark plug, slide the gapping tool into the gap until it fits snugly, then read the gap distance on the tool.

Step 3

Key in the number of centimeters into the calculator. Press the multiply key. Enter 30,000. Press the equals key. The result is the voltage required to produce a spark in the gap. For example, if you measure 1 millimeter, first convert to centimeters. At ten millimeters per centimeter, you'll have .1 centimeter. Multiply .1 by 30,000 to get 3,000 volts.