An electric adapter for a notebook computer (converting 110 volts to 19 volts) o

Question

An electric adapter for a notebook computer (converting 110 volts to 19 volts) operates 10oC warmer than the surrounding temperature.

Determine the sign of the interactions between the system and its surroundings:

Electric work out : Negative / Not enough data to decide / Positive / None

Electric cork in : Negative / Not enough data to decide / Positive / None

Mass interaction : Negative / Not enough data to decide / Positive / None

Net work : Negative / Not enough data to decide / Positive / None

Heat interaction : Negative / Not enough data to decide / Positive / None

Explanation / Answer

The important points to note in the given problem is that the electric adapter takes energy from the power supply, does work by providing power to the notebook and rejecting some amount of heat to the surrounding(this is why it gets heated up and feels warmer).Actually, rising temperature shows the increase in internal energy of the material in the adapter.

electric work out is the net work done by the adapter, i.e. energy taken from the power supply minus the energy lost in heating itself, which is positive since we know that the adapter is powering the notebook.

electric work in is negative of electric work out.

No net amount of mass is entering or leaving the system so the mass interaction is zero

Net work is positive since total energy taken minus energy lost is positive.

Heat interaction is positive since heat is rejected to the surrounding as it gets heated up.

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