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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answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.