Information given: Heater 220 Volts and 1200W Question: How many joules electricity will a heater use per second?
The Joules is the unit of measurement of work. The rate at which the work is done is measured in Joules per second, or Watts, and is called power:
`P = (DeltaW)/(Deltat)` .
For an electric device, the power can be calculated by using a current going through this device (I) and applied voltage (U), and/or resistance of the device (R).
`P = IU = I^2R = U^2/R` (The last two relationships are obtained by using Ohm's Law, which relates current and voltage: U = I*R.)
In this question, we are given that the heater is meant to use is the voltage of 220 Volts, and the power it will use is 1200 Watts.
Since a Watt is a Joule per second, then if the heater is indicated to use 1200 Watts, this means it uses 1200 Joules of electricity per second.