How does the law of conversation of energy apply to machines

Energy can neither be created nor destroyed but can be transformed from one form to another in a machine with loss in energy in form of heat.

For example, in a machine (mircowave), electrical energy which is a form of energy is transferred to the machine to create thermal energy to warm or defrost food, during this process, energy is converted but not created. The total energy given to the machine is equal to the energy given out by the machine plus energy loss in form of heat.

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