$3)$ Think of an example $($any source or process, hypothetical or real$)$ in which the change of energy is approximately $1$ J. Give another example in which the energy changes by $1$ kJ$,$ and a third where the change is $1$ MJ$.$

 

$4)$ Give examples in which the power involved is approximately $1$ W$,1$ kW; and $1$ MW$.$