The Otto cycle is constructed out of: TOP and BOTTOM of the loop: a pair of quasi-parallel adiabatic processes LEFT and RIGHT sides of the loop: a pair of parallel isochoric processes The adiabatic processes are impermeable to heat: heat flows into the loop through the left pressurizing process and some of it flows back out through the right depressurizing process, and the heat which remains does the work. The processes are described by: A P-V animation of the Otto cycle is very useful in the analysis of the entire process.