Home >> Science & Nature >> Science

How to Calculate the Energy Contained in a Spark

The energy in sparks varies widely, from the tiny shocks you get in the winter from touching a doorknob to lightning strikes. The amount of the electrical charge, multiplied by its voltage, equals the energy. Scientists measure charge using units called coulombs, where one coulomb is the charge from one of current flowing for one second. Small sparks last a fraction of a second, and they have currents of millionths of an amp. Estimate a spark's voltage by measuring the distance of the spark gap, and calculate the spark's energy by multiplying the voltage by an approximation of the charge.

Instructions

- 1
  Turn off the spark equipment, if necessary.
- 2
  Measure the spark gap with the ruler. Enter the measurement in decimal inches into a calculator. For example, if you measure 1/4 of an inch, enter it as 0.25. Press the "Multiply" key.
- 3
  Key the number 60,000 into the calculator. This is the approximate voltage per inch of separation for spark gaps. Press the "Multiply" key.
- 4
  Key the number .00001 into the calculator. This is 10 microamps of current. Press the "Multiply" key. Enter the number 0.01 -- this is one one-hundredth of a second, the approximate duration of the spark. Press the "Equals" key. The calculator will display the energy of the spark in joules. For this example, 0.25 inches x 60,000 volts per inch = 15,000 volts; 15,000 x 0.00001 amps = 0.15 watts. 0.15 watts x 0.01 of a second = 0.0015 joules of energy.

Science